Resisting the temptation to answer this in a comment... But yes, please, let’s write answers instead of comments (of course the users most likely to answer questions in comments are unlikely to read this).

This is probably included in the “peer reviewed” part of your question, I think it’s worth expanding on: comments are not peer reviewed, and I see lots of wildly incorrect comments which end up getting upvoted somehow with no easy way to react (a response in a long list of comments is pretty much invisible, especially in reaction to an upvoted comment). A good rule of thumb for comments relates to the reasons they can be flagged for deletion (offensive, obsolete, or in need of moderator attention; this doesn’t explicitly include “utterly bonkers”): basically, only write a comment if there’s a clear path to its removal, i.e., you’re asking for or providing further information which will result in an edit to the question or answer, and the removal of the comment (either by its author, or by a moderator after someone flags it as obsolete). Note that this also applies to “further information”-style comments; I tend to comment as a suggestion of extra information the author might want to include, in cases where I don’t feel comfortable just editing the question or answer. (See this answer for a recent example. I think the information is relevant and useful, it’s just not obvious to me how to include it verbatim in the answer without making the answer harder to read.)

I also think in general we should all get used to editing questions and answers more; I certainly found it enlightening the first few times Gilles and Stéphane edited one of my answers for me, instead of either commenting on it or adding their own answer. The whole point is to get the right answer to affected users (plural, not just the OP), in the safest way possible, and the most educating way possible (without drowning the reader in detail); reputation points and badges don’t matter in the grand scheme of things. (That’s much easier for high-rep users to say obviously, but if you’re active enough on the site to be editing questions, reading Meta and generally thinking of janitorial duties, reputation will follow.)

Finally, it would also be great if we could review our questions, answers and comments every once in a while, and merge any relevant comments, flag them as obsolete, and delete our own obsolete comments. If you’re afraid deleting your own comment will make the surrounding ones harder to review, don’t be, flag the surrounding comments: moderators can see deleted comments, and they’ll take the whole context into account when reviewing flags (most of the time).

Resisting the temptation to answer this in a comment... But yes, please, let’s write answers instead of comments (of course the users most likely to answer questions in comments are unlikely to read this).

This is probably included in the “peer reviewed” part of your question, I think it’s worth expanding on: comments are not peer reviewed, and I see lots of wildly incorrect comments which end up getting upvoted somehow with no easy way to react (a response in a long list of comments is pretty much invisible, especially in reaction to an upvoted comment). A good rule of thumb for comments relates to the reasons they can be flagged for deletion (offensive, obsolete, or in need of moderator attention; this doesn’t explicitly include “utterly bonkers”): basically, only write a comment if there’s a clear path to its removal, i.e., you’re asking for or providing further information which will result in an edit to the question or answer, and the removal of the comment (either by its author, or by a moderator after someone flags it as obsolete). Note that this also applies to “further information”-style comments; I tend to comment as a suggestion of extra information the author might want to include, in cases where I don’t feel comfortable just editing the question or answer. (See this answer for a recent example. I think the information is relevant and useful, it’s just not obvious to me how to include it verbatim in the answer without making the answer harder to read.)

As pointed out by Eliah Kagan in the chatroom, this is all just a re-hash of the help page explaining comments.

I also think in general we should all get used to editing questions and answers more, if necessary explaining the “why” in the change description; I certainly found it enlightening the first few times Gilles and Stéphane edited one of my answers for me, instead of either commenting on it or adding their own answer. The whole point is to get the right answer to affected users (plural, not just the OP), in the safest way possible, and the most “educating” way possible (without drowning the reader in detail); reputation points and badges don’t matter in the grand scheme of things. (That’s much easier for high-rep users to say obviously, but if you’re active enough on the site to be editing questions, reading Meta and generally thinking of janitorial duties, reputation will follow.)

Finally, it would also be great if we could review our questions, answers and comments every once in a while, and merge any relevant comments, flag them as obsolete, and delete our own obsolete comments. If you’re afraid deleting your own comment will make the surrounding ones harder to review, don’t be, flag the surrounding comments: moderators can see deleted comments, and they’ll take the whole context into account when reviewing flags (most of the time).