This meta question raises two very different topics that I think are worth exploring at some length: whether questions about punctuation are inescapably opinion-based and therefore off-topic at English Language & Usage; and whether it is appropriate or inappropriate to ask a question at EL&U with the intention of answering it yourself.
Punctuation questions as questions of English language and usage
If you spend any considerable length of time at EL&U, you become aware of the prevailing view here that "English language" refers to spoken English and that written English is merely a more-or-less flawed system of recording actual (spoken) language. In this view, matters of orthography and punctuation, in particular, are mere trappings of the language—not things to be understood as having "correct" or "incorrect" status in any scientific sense.
For this reason, questions framed in terms of correctness—as in "Is 'thru' an acceptable alternative spelling for 'through'?" and "Is it okay to end a series of simple declarative sentences with exclamation points (for example, 'I went to the store to buy a loaf of bread! They were out of rye, so I had to buy pumpernickel! The price was about the same, though!")?"—inevitably run afoul of review queue reviewers because they invite primarily opinion-based answers.
But if punctuation questions framed as matters of correctness are doomed to be read as solicitations for opinion-based answers, does it follow that all punctuation questions are inherently and unavoidably off-topic at this site? I think not.
It's easy to undervalue matters of orthography and punctuation as critical components of communicating a language—because it's easy to undervalue the extent to which people depend on writing in such communication. As far as I know, I've never spoken a word to anyone who regularly visits this site, and yet I've read and written many thousands of words from and to site participants. It thus seems arguable, at least, that the fundamental language by which we communicate at English Language & Usage is written English, not spoken English. And because we lack the ability to rely on vocal cues, timing cues, and visual cues to help convey our meaning, we must depend to a considerable extent on the regularity of the spelling and punctuation we use to convey our meaning clearly and accurately. Indeed, regularity in the forms of spelling and punctuation that we use may be more important to coherence than the particular forms spelling and punctuation that we adopt.
Many people who ask questions about correct spelling or correct punctuation suppose that there is a universal right and wrong about these matters, which makes it easy to dismiss their concerns as being based on a fundamental misunderstanding of the nature and purpose of spelling and punctuation. There is no Academy of Proper Written English, we tell them, so any view of what is right in these areas is ultimately arbitrary—and then we close their questions.
Often, however, a predominant convention exists in written usage regarding a particular matter of spelling or punctuation; and even when there is strong disagreement over how to handle a particular situation, one may be able to identify a distinct and definite range of possibilities that enjoy substantial real-world support. People care about predominant conventions of spelling and punctuation for the same reason that they care about predominant conventions in word meanings: they want to express themselves clearly and avoid being misunderstood.
I think that questions that ask about predominant forms of punctuation usage, widely supported alternative forms, and ranges of established options are legitimate questions of written English usage and can be objectively answered by citing evidence drawn from multiple style and usage guides and—in cases where predominant usage is clear—from levels or degrees of real-world usage. Some people writing in English do write in all-uppercase or all-lowercase letters, for example, but it is not merely a matter of opinion that most people writing in English use a combination of uppercase and lowercase letters and do so in accordance with various identifiable and consistent conventions.
With regard to how to ask a question about punctuation in a way that maximizes its chances of surviving the review queue without being closed, my advice is to frame it in a way that inquires into real-world usage (for example, "Under what circumstances do English-language writers and publishers commonly omit an open quotation mark in a phrase, sentence or block of text in which they include a close quotation mark?") or into the range of available style manual advice (for example, "In what circumstances (if any) do style guides approve of omitting the open quotation mark of a pair, despite including the close quotation mark?") Neither of these questions asks for an opinion. One asks for factual information about predominant usage in the wild, and the other asks about the (possible) range of advice that style guides—a category of widely used normative reference works—offer on the topic.
Asking a question that you want to answer yourself
Every now and then, I think of a question about English language and usage that I would like to investigate. My first step in such instances is to search the EL&U archives to see whether someone else has already asked it. If so, I check the answers to see whether they dispose of my original question. If they don't, I research the issue myself and, if I uncover something that seems worth sharing, post an answer myself.
Sometimes, however, my question is sufficiently different from one that has already been asked and answered on EL&U that it doesn't make sense to shoehorn an answer to it into the existing question. And sometimes no one at EL&U has asked anything remotely similar to my question.
In those cases, I do some preliminary research to see whether my question shows signs of leading somewhere interesting. If it does, the next decision I have to make involves determining where and when to cross over from presenting the question to composing an answer. This is not an easy matter to resolve. In the old days of EL&U, you could lay out the question in a paragraph or two and then start trying to answer it. But in order to escape the review queue in one piece under the show-research regime, you have to present some account of some amount of research that you've already done toward answering the question yourself—and there is no bright line between research that establishes the legitimacy of a question and research that helps provide a thorough and nuanced answer to it.
In some instances, I end up doing all of the research into a question that I can before posting it. Then I go back and break off my account of the research at a certain point, posting part of it in the question and the remainder as an answer. This can result in the question and the answer going up on the site within minutes of each other.
In other instances, I find a natural stopping point for the question part of the research and post the question before proceeding with research into an answer. In those cases, I may not post an answer for several days—or ever—even though I had intended to do so. And of course sometimes another EL&U participant will offer an answer that is better than the one I've been working on, at which point I'll either abandon the answer or post parts of it as supplements to the better answer.
One thing I have never been tempted to do is to give my own answer a green check mark. In the first place, practically all of my answers—and certainly all of my answers to my own questions—rest on publicly available information, rather than personal expertise of some kind. Consequently, my answers aren't definitive; they merely present the results of the research I've done and are limited by the shortcomings of that research (e.g., limited access to various archives; failures to look in the right places; errors in interpreting the material I do find). And as with editing your own writing, assessing the comprehensiveness and value of your own research is a minefield in which the bombs are buried precisely where you are least likely to detect them yourself.
Also, the green check mark is essentially a thank-you to a poster who has taken the time to provide a strong answer to a question you've asked. I still regret not having accepted a good answer to one of my questions, which, I suspect, led the poster to withdraw the answer at some point. In any case, there is an element of absurdity in thanking yourself for answering your own question well. If you feel strongly that your answer is the best of the ones your question has elicited, my advice is to refrain from accepting any answer—just leave it to the community of upvoters and downvoters to rate them.
One goal of EL&U is to provide well-informed answers to good questions asked by people who don't know where to find those answers themselves. Another goal is simply to provide well-informed answers to good questions. In the latter case, it doesn't matter who asks the question; it only matters that the question and the answer(s) are worthwhile. It follows that you should not avoid asking good questions and trying to answer them yourself at this site.