I’d say update the post and leave the old link in the text for posterity.
Yep, make a note in the post body about the change, so that people have context for comments on the old article
This depends on how different the new article is
I think you should link the better article in the comments or in an appendix to the post text.
A post that is about an article should remain pointed at that article, in my opinion. It’s a matter of referential integrity.
Edit the post to say better link in comments and put the new one there. Leave the original alone.
I’d say since Lemmy supports link posts with post text, you could also just put the link in the post text itself rather than comment it
IMO it’s ok as long as it’s clear what’s happened - i.e you make a note in the body of the post
But, the age of the post and the number of comments make a difference. I wouldn’t edit a post more than a few hours old myself, or that has lots (subjective) of votes; and especially not if it has lots of comments, and especially especially not if the comments talk about specifics of the original article.
5 mins after originally posting with 1 vote and no comments: fine
2 days after originally posting with 1k votes and 100 comments: probably not fine.
in the middle of those extremes: grey area, use good judgement, expect pushback
tl;dr - depends
