How to remove a discussion I posted?
If a discussion has no replies you can delete it via the menu on the right. If it has replies you cannot.
I see that your only discussion is https://forums.adobe.com/thread/1820138 - what is the reason that you want to remove it?
The information in the topic may be useful to other users, so discussions are not usually deleted. Eventually when there is no activity for a certain time, the discussion will automatically be archived.