Should be edit, not comment
Simple spelling, grammar, name, etc issues should result in an EDIT not a comment.
Use the moderators
If you want to delete your no-longer-applies comment and other spurious comments depend on your comment then flag both comments for moderator attention. They will view them, see the fix has been applied, and delete them if they feel they no longer add anything useful to the question.
Is it appropriate - a philosophical treatise
Specifically for your case, leave it. It lends a bit of history and interesting information to the site (I always pronounced it "I R fan view") which I think adds to, not detracts from, the question and answer.
In general, however, I don't thinks it's appropriate or inappropriate to leave out of date comments. If the comment is out of date, and no one else's comment depends on your comment, then there is little reason to keep it, but there's no pressing need to delete it either.
If, as in Paul Tomblin's case, the comment is out of date, other comments reference it, but the comment itself no longer adds to the question, then again, there's no need to delete it, but it isn't going to ruin the comment reader's experience if you do. They will quickly understand that there's something missing, but based on the existing comment it's not important. They can check out the edit history of the question if they are curious what the change was.
If the comment is at all useful, or interesting, even from an historically outdated perspective, I'd say err on the side of keeping it.
There is some undercurrent against spurious comments on SO, so if it's exactly 50/50 for you, then err on the side of deleting it.
Remember - you own the comment. It's not editable at all, or deletable by anyone else except under some circumstances, so unlike questions and answers it's not a community post. It's uniquely yours, and so its life or death is completely up to you.