I think what they're talking about is:

1. The Emperor being Balduran, which I find to be a bit excessive and doesn't add much to his character, but the worst it does is retcon Balduran to being an Elf (or Half-Elf) than Human.

2. Durge kinda contradicts Bhaal's return to be a few decades earlier.

This post, which is a long read, goes into these two (and much more) in more details:
https://forums.larian.com/ubbthreads.php?ubb=showflat&Number=904814&page=1

3. Viconia and Sarevok's mischaracterisations, seen more here: https://forums.larian.com/ubbthreads.php?ubb=showflat&Number=904425&page=1