Bittorrent Mainline DHT and Tor

[Cathal Garvey]

Hey all,
I'm aware that (for pretty good reasons) bittorrent is "blocked" by most 
exits on Tor. However, I'm unsure how this blockage is implemented, and 
it just emerged as a relevant item in my thought-process: the Bittorrent 
"Mainline" DHT is not necessarily useful to Bittorrent alone, but is 
frequently used as an experimental platform for other P2P applications.

Is the bittorrent DHT blocked by Tor exits, or just the Bittorrent 
file-transfer protocol? If the latter, how is that block enacted when 
most bittorrent apps support protocol obfuscation and dynamic ports?