The only difference I’ve found between pure SMF and WP + bbPress is in the replies and as you can see there’s a difference between user info in the start of a topic, and in the reply.
If you look at https://www.svenskaflippersallskapet.com/index.php?topic=26595.0 (correct)
and compare with https://svenskaflippersallskapet.com/devo/forums/topic/lincade-onsdags-oppet/ (the reply differs).
I will look more into this and see if I can find other faults, but as for now, this is the only.
Sorry for the fuzzyness. The replies are the ones that displays wrong usernames.