Some style guides, including the most widely influential ones in the Unites States, disapprove of hyphenating compounds of the type "commonly available." The advice in The Chicago Manual of Style, fifteenth edition (2003), is representative:
7.87 Adverbs ending in "ly." Compounds formed by an adverb ending in ly plus an adjective or participle (such as largely irrelevant or smartly dressed) are not hyphenated either before or after a noun, since ambiguity is virtually impossible.
So publishers and publications that follow Chicago's style guidelines don't hyphenate phrases like commonly available—and anyone who favors a minimalist approach to punctuation (that is, an approach based on the idea that punctuation is appropriate only when omitting it might damage the clarity of the writing) may find Chicago's rationale persuasive.
But it's just a style guideline. Hyphenating commonly-available does not damage the sense of that phrase, any more than hyphenating to-morrow damages the sense of that word. As long as the text consistently applies the style choice its author or publisher has made, I as a reader have no trouble adapting to that approach. Readers who can't get over their hostility toward a consistently applied style that differs from the one they personally favor are, I think, their own worst enemy: They let their insistence that some minor style decision is wrong divert their attention from the substance of the content they are reading to something that is ultimately arbitrary and trivial.
The poster's criticism of off-topic finds far less support in style guides than his criticism of commonly-available does. Unlike phrases of the type adverbly adjective, which Chicago (among other style guides) recommends leaving open regardless of where it appears in a sentence, a term like off-topic normally (for clarity) takes a hyphen when it appears before the associated noun (as in "off-topic question"), and Chicago is far from categorical in its endorsement of leaving such terms open when they appear after the associated noun:
7.86 Compound modifiers before or after a noun. When compound modifiers (also called phrasal adjectives) such as open-mouthed or nicotine-free come later in a phrase than the noun they describe, ambiguity is unlikely and the hyphen dispensable (though not incorrect). When such compounds precede a noun, hyphenation usually makes for easier reading. ... Hyphenated adjectival compounds that appear in Webster (such as well-read or ill-humored) may be spelled without a hyphen when they follow a noun.
The gist of 7.86 is that compounds of the off-topic type "may" be spelled without a hyphen when they follow the associated noun, but are "not incorrect" if spelled with a hyphen.