Let's say I have a bunch of tickets connected to conversations, lets say the ticket type is "bug" and it's for bugs. Now if I wanted to tag all "bug" conversations in bulk, I couldn't. Because if I select them all and edit in bulk to add these tags, the system won't tag the tickets, as tags only work in conversations. This messes with bulk actions enormously.
So we should be able to either 1 - tag tickets too, or 2 - bulk editing tickets to add tags, the tags should get added to the conversation that is connected to it.
Tagging tickets sounds like the best, though, because then reports can be made based on the tags for them too.
