Who enabled slow mode, and does it apply to TL4 users?

I think this is something that should be discussed in the Staff category on your instance. If moderators aren’t communicating with each other, that’s not really something that the software can solve?

You might also have a topic for your community to discuss slow mode, what it is for, how it works, etcetera.

As far as

Please wait 2 hours between posts in this topic

I don’t feel

Please wait 2 hours between your posts in this topic

is really necessary? No other community that I’m aware of has interpreted it this way? It’s kind of .. nonsensical.. to have a topic where one random person gets to post, then everyone else has to wait two hours? That just doesn’t make sense?

I feel that’s fairly self explanatory copy. You must wait 2 hours between posts in that topic. If you feel the copy should be different for your community, you can edit that copy – or any copy in Discourse – via Admin, Customize.