I think that that might come down to the Akismet service, not sure that anything can be done about that.
Should an edited post be marked as unread again?
I feel that an edited post should be changed from read to un-read status therefore showing up again in the
Recentthread displays. Why do I ask this? I posted a new topic in the tech support category which then had a handful of 'reads.' I have since added a lot more content to the post and now those people who have already read my post will not realize that I added more content. Maybe an elegant way to handle this would be if greater than x% changes (significant content change) change the post status to un-read but if less than x% changes (maybe just a few typographical corrections) leave the post as is.
What is your opinion on how to handle edited posts?
Also could be abused to keep posts on top of recent without anybody realising
I think this should be some kind of feature that you can enable as Admin for X groups, because I consider this is a good idea if you want to make a Topic to have relevant and persistent information especially if its posted by someone in the "Announcers" group or groups that have some kind of purpose on the Forum.
@rod general practice is not to edit posts to add more information but make new post with the additional information. editing is more for typographical corrections.
This. Definitely shouldn't make it unread, leave it with last edited. (Unless you're one of those that follows topics,,then you could maybe have "user has made an edit in topic."
The author also could create a new post stating that some changes have been made if it's worth an update in his opinion. I don't think any other concept is needed since editing posts is more wiki-like than forum-like. If your forum relies on something like this you might consider using a wiki platform instead or additionally.