Thread Code Help

Does anyone know what sanitation is being applied for the thread code? I feel like I'm slowly losing my mind trying to find what elements and styles it's going to arbitrarily rip out.

Can't use proper HTML5 elements (div, header, aside, etc), gotta use tables which is putting me right back in 2010 and reminding me why I hated forum table skinning, but on the more baffling side it seems to refuse to use certain styles, like border-radius and overflow.

I know Lila made a post breaking down some of the HTML that you can use, but I'm struggling to find what styling you can and can't use in threads. If anyone has a list or know what library/tool Wolvden's using, it'd be much appreciated ;___;

And big kudos to all y'all out here making gorgeous threads within these limitations, you the real MVP.