Recently there was a discussion about removing previously created synonym of some tags, so that the two tags are separate again. (And we could probably find several related discussion in the past.)
My first question is how is this done. Is it something moderators can can do? Or is some action from SE staff needed?
Another question is what happens when the synonym is removed. We have many questions tagged (master-tag). Some of them might have been tagged by (slave-tag) at the time when the synonym was created. Some of them might be tagged (master-tag), but they got this tag after a user explicitly typed (slave-tag) when entering the tags.1 After removing the synonym, do all question keep the (master-tag)? Or do some of the questions get the (slave-tag)? (For example, the two types of questions mentioned before seem like a reasonable candidates.)
Last question: Does it make a difference whether the two tags have been merged2 or only synonymized?
1Number of such posts is shown in the list of tag-synonyms.
2See here for explanation of the difference between these two options. Based on the answer to the following post, it seem that there might be a difference: Need a rollback/undo for tag synonym merging.