Quinn's passive (Harrier) is marking targets even when Quinn is concealed
Before the rework, Harrier didn't mark targets when Quinn was concealed. It's a pretty obvious giveaway that Quinn is nearby if you randomly get marked with Harrier.
Post-rework, it's happening consistently - Valor passively marks targets whether Quinn is stealthed or not. It wasn't documented as far as I know, and it's a really irritating change. I don't think any other champ mechanic works like this.
Smaller bug: Valor's passive Harrier marks get removed when a new Harrier mark is added by Q or E on another target. Marks set by Q or E do not get removed (unless you apply them to the same target).
UPDATE: Bumpity bump. This is still happening 2 (3?) patches later. I know you guys don't respond to every note (and I don't really expect you to) but I've seen this bug reported multiple times in multiple places, including the boards, Reddit, Twitter, and in the Q&A roundups that have happened, but I've never seen a Rioter acknowledge that they know about it.
I guess it would mean a lot to me to even know that this but was at least on someone's list, even if it's not being actively worked on right now. It's a small but very irritating issue with Quinn's kit right now.