Prevent users from posting ineffective @mentions while editing a post
At the moment, there is no indication whether a mention will be "effective" (i. e. it will actually trigger notifications).
This lead to confusion among our users, who intended to trigger a mention by editing an existing post, what - of course - currently doesn't work.
There are two possible solutions to this:
1) Show users a warning, when their @mention will not have any effect
This could be along the lines of: "You can't trigger @mentions by editing an existing post. Please write a new post if you want to mention someone."
2) Make edits trigger mentions
This would also circumvent the problem, that if you want to make people aware of your post but you forgot to mention them, you have to repost the complete post so useful information shows up in their notification email (and not just the @mention text). You could also point specific users to older posts without reposting.
I'd like to hear your arguments for suggestions 1) and 2) because I'm really not sure what the better solution would be. (I tend to favor 2) because it requires less warning texts and is more "intuitive", I guess. But maybe there are huge downsides I can't see right now.)
Marcus Mangelsdorf commented
One potential downsides of actually making edits trigger notifications would be the possibility of duplicate notifications, if the feature is implemented too naively.
To prevent annoying multiple notifications if the mentions weren't actually changed/added, editing a message would have to compare the list of mention-keywords before and after the edit, and then not trigger new notifications for keywords that exist in both lists.
I see now, how this adds quite some complexity, since users can define arbitrary words to be notified. Maybe the simplest solution would be to really just look at explicit @mentions when committing an edit and don't trigger notifications for arbitrary keywords during edits.