After some careful thought (as much as that is possible), I have ruled out (for now) Isaac and FT, as they at the very least participated in discussing the options. I do not agree with ? that FT's suggestion is anti-town, as any strategy on Day 1 can be seen as such, but at the very least it's information, and information is always good. In addition, Isaac usually gets more verbose when he's Scum than when he's Town, so there's that.

Yuna is quiet, but I've never seen her differently in the few games that I played, until she's accused - so nothing different.

Both ? and ranagrande had been quiet for a while, but the one was RBIRL for a while (although that does not excuse the first couple of days) and the other excused himself.

Beet displayed a lack of knowledge of the setting (saying it was Tintin), which is either not the smartest thing he's done (Isaac and me did the same strategy by Googling Champignac (and the count's name), which makes it quite clear what the setting was - I just asked Isaac in the hope he would say that he recognized/Googled his character's name, which would indicate a recurrent character), or a deliberate ruse to make us believe he had no idea who the character is, which would make him a likely Scum.

So, I would go with beet.