Duplicate posts on the forum are not uncommon and they’re often taken down (rightfully so), however, for certain categories like #development-discussion (or even #forum-help), I believe it would be better to merge duplicate topics into one existing post.
Currently, what I do when I encounter a duplicate post is simply link to existing topics underneath the main post, however, like I said before, if a new discussion is created under the duplicate, they’re lost/ended when the topic is eventually closed.
I don’t know if this would be possible to implement, but if it were, this will allow developers to continue their discussions whilst removing an unnecessary new topic: keeping the forum clean.
We try to do this sometimes but often it messes up the flow of conversation and is not really appropriate or respectful towards the posters of either thread. It also mangles the time ordering of the replies. You might see us opt not to merge in many cases for this reason.
For things that don’t break rules (duplicate bug reports, duplicate feature requests), there should be a link between the posts in the closure note so that you can hop between to see the comments of either thread. If this does not happen currently (moderator does not add such link or they unlist the thread instead of keeping it listed), please DM me some example cases.