I think that's appropriate, as long as it doesn't leave a more obtrusive mark on the comment itself than is already used.

It doesn't happen very often, but it is quite irksome when someone edits their comment so my reply doesn't make sense.

You're probably okay as long as you quote the bit you're answering.

That may be a general problem, but on Less Wrong, what I typically observe is that people get upvoted for accepting counter arguments and changing their mind and for apologizing for rude behavior. Sometimes downvotes are even removed from the rude comment that required the apology.

Even so, it's still much better from a status perspective for people to forget or not to know about "bad" comments if possible.

Though you will also observe that people often don't delete their mistakes, and explain them instead. I myself have done this more than once; and in fact I have become somewhat self-conscious about editing comments since I found out about the asterisk that results (which I went nearly two years without noticing).

Nevertheless, I derive significant comfort from knowing that I have the ability to "rewrite history" if I really need to.

Also, it would be undesirable to have a bunch of new comments of the form "I've changed my mind about that semicolon". Such comments might even be downvoted, resulting in a no-win situation for the commenter.

As I have said, that is a fair use of the edit feature. But it is not the use that you were defending.

If that's what you thought, then you misunderstood, because it most certainly is (among) the use(s) I was defending. I see a quantitative continuum between this kind of revision and more substantial kinds, not a qualitative separation.

And you're not actually editing recorded history.

That seems to me to deny basic facts. The comments are a record of a discussion, editing them to say something different destroys that record.

It destroys that record, but there's nothing stopping anyone else from keeping another record and preserving the content themselves -- the simplest way being to quote the comment in reply. And even the most notoriously deleted posts and comments ever to appear on Less Wrong are currently preserved off-site.

The argument that to revise is to rewrite history applies Fully Generally against any kind of revision of any public document. Should blog authors not be allowed by blogging software to edit their posts? In fact, why should anyone be able to delete their account on LW at all? Even making comments anonymous destroys part of the historical record, namely the information about who wrote it.

However I think that archiving previous versions while allowing revisions is probably an acceptable compromise (provided the archive link is unobtrusive and perhaps slightly inconvenient).

People who generally write high quality comments are not going to hemorrhage enough karma from their momentary mistakes to put them under any thresholds. Once you are above 20, additional karma is just license to screw up.

Karma is also a proxy for status, and in fact it's the hemorrhaging of status that I was most concerned about. And flurries of bandwagon downvotes on old comments have happened more than once, including to me.

It doesn't happen very often, but it is quite irksome when someone edits their comment so my reply doesn't make sense. (And it tends to happen more often in more heated discussions.) I expect this to happen more often as Less Wrong attracts more members and the level of the median member goes down, even as the level of individual members goes up over time after they join.

I'm not sure why you would expect lower-level members to edit more than higher-level members.

That seems to me to deny basic facts. The comments are a record of a discussion, editing them to say something different destroys that record.

Currently, the record can be destroyed by deleting it, so I don't see this as a big deal.

It doesn't happen very often, but it is quite irksome when someone edits their comment so my reply doesn't make sense.

That's often a compliment.