Can I set forum permissions so only a role, plus the OP can reply?

I am trying to configure a Q&A forum, where all members of the community can post a question, but only those in an expert group can reply AND the person who posted the question can reply.

So far, I have only been able to configure such that ALL members can reply, or JUST the experts can reply. 

This is no good, because when the expert replies, it is inevitable that the OP will sometimes want to ask them more detail about their reply. 

If this is not possible on 10*, is there any workaround, or would it be possible to configure the forum to work this way in 11? (it occurs to me that there might be an automation for that in 11 where one could say: if this person posts a question, then put them in a role which allows them to reply to their own thread, or something, but that would need to apply only to the specific thread. 

Parents Reply Children
No Data