I generally feel the same as what Dan Bron said in his comment: I prefer that new or changed material be integrated seamlessly into the original post so that it can stand alone instead of calling attention to how it evolved, but I recognize that occasionally a big fat marker calling for a second look and re-evaluation of the question can be helpful.
For your in-post example (about fixing a typo), I completely agree that calling attention to the fact that you fixed something trivial is entirely unnecessary; that sort of comment goes in the "edit explanation" box, not in the post.
For your real-world example (originally this deleted post's edit history, visible to 10k+ users only), I think you could have tightened up the added material a bit, but should not have rolled it back completely; the OP was trying to add material clarifying the specific source of concern for the question. As originally written, it was an "unclear/too broad/proofreading" sort of question; the edit narrowed the focus down to "how do I correctly punctuate this type of clause". (Which I agree was still an entirely closeable question, but there was at least an attempt to improve it.)
As a general guideline, I would lean toward the same rule of thumb as the "thanks" situation: if you see a post with some form of "thanks" at the end or an "edit:" marker, don't just pop in, remove that, and move on; take the time to look the entire post over and fix other small flaws that you find. If you can't find anything else that needs fixing, leave it.