Here's how we're using the tags right now:
- We have 15 questions tagged both transitive and intransitive.
- We have 7 questions tagged transitive only.
- We have 6 questions tagged intransitive only.
Most of the questions that have only one tag or the other seem to be about transitivity in general, or are confused. For example, this intransitive-only question is really about transitive verbs―the OP is making a common mistake, confusing transitivity with the phenomenon we see in verb pairs like 教わる・教える. This intransitive-only question is really about transitivity, and this intransitive-only question is about both transitive and intransitive verbs.
It seems like it'd be better in almost every case to merge them into one tag.