Not sure how much you're interested in these kind of things because a lot of them are kind of obscure and something only people deliberately trying to break things would encounter, but here's what I found.
This is all femPC/conspiracy path with 14.11b + the additional patch:
Using load from file off the starting page returns only a blank page if the save to be loaded was made in the severn valley mod. The only way I've found to load it is by first starting a new game with the mod enabled and then loading it again.
The color theme doesn't seem to be saved. I use white but it always loads as dark gray.
If you don't have the book (for instance, if you left it in your room), asking Tess to help you look something up (the option chain that leads to learning pass) silently fails. It should probably explain you need the book to learn spells or something, since at this point in the dialogue it's not even obvious that's what you trying to do.
If you give Beasley the book once you have protection from magic, then charm him, he'll tell you that the DA gave him the book. You also have to leave and re-enter his room to have the option to get it back. If you then ask for it, you'll immediately have the option to give it back to him and if you do, the whole cycle repeats. If you remove your magical protection before giving it back, you can end up charmed by a charmed Beasley. On top of that, the actual bad ending seems to be inaccessible as the "what was that he said" button does nothing and you're stuck on that screen.
If you free Mrs Robbins with the silver ring, then enter the bedroom, you have the option to tell Tina that her mother's okay now. If you do, you get the option to ask if she can take mana from other people despite having no reason to know she can do that.
Teleporting while invisible doesn't show the clickable list of places along the side, so you can only pick your destination via the map.
If you leave the book in your room before doing the ritual, when you wake up in the hospital you're somehow alarmed by its absence and know it's been taken.
I had the option to ask Beasley where Davy has gone after teleporting into the school on a weekend.
Recharming Betty plays one of Ash's charm scenes.
If you turn invisible in the museum, the only option is to exit. If you do it while possessing Gina, you can't even do that, and the menu is entirely empty besides ending one of the spells. IIRC I could walk around before I stole the vase, I think?
While possessing a charmed Gina at her house, one of the choices is "have her join you in the bath", but you're not there.
While possessing a charmed Gina at the museum, you still "see your slave Gina waving to you and gesturing towards a door, the security office it seems". And basically nothing about the scene makes sense if you then charm the museum curator while possessing Gina.
"Karley's Salon is a women only salon and the owner does not hesitate to tell you that. She does not force you to leave but it it clear that she does not want you there." This shows up even for femPC.