Re: Changing Topic ID
Note that many plugins use their own tables to keep track of information based on topic_id and post_id because of the poor performance of bbpress meta (non-unique index and large string storage).
Currently there is nothing in the bbPress API that allows a plugin to hook to be notified when there is a topic_id or post_id change to an object. So all plugins in existence (and bbpress itself) assume this will never happen. The only thing bbPress accounts for is a forum_id change on a topic/post and I am not even certain there’s an API hook for that.
This means if you manually change a topic or post id, and you have plugins which store meta for those items, you’ve just broken your data in a way that cannot be rebuilt later. All the recounts in the world won’t fix the problem.
So keep that in mind. Things like attachments, polls, etc. are all affected by what you are talking about if those topics have such meta.
(this is also specifically why I tell people not to use the Move It plugin)