It would be so helpful to have a way to merge tags, as tags end up all over the place.

Via the backend, if you could select multiple tags, then click "Merge...", then be presented with a UI for "specify the tag that these should merge into" and you can choose one of the tags already selected, or create a completely different one. There would also be the option to "add new tag" or "strip and replace". If add new tag was selected, then any discussions with any of the tags would have the new tag added as an additional. If strip-and-replace were selected, then any discussions that had any of the old selected tags would have those tags removed, and the new tag would be assigned to all of the discussions.

Would be a HUGELY useful feature for managing large discussions!