This won't make much sense, but it's true.
Bayonet are perfectly legal on the Russian SKS (gets kinda "iffy" if it's been removed), & are generally a no-no on the Chi-Coms.
I can't remember exactly how the BATF decided that (I've got a letter from them around here somewhere, I'll post it if I can find it). I think it had something to do with the Chinese ones not qualifying as C&Rs, because they cranked so many out until recently.
FWIW, bayonets are also legal on the Romanian SKSs. AIM, & SOG (page 3) still have them in this month's flier, but they're not $159.00 anymore - both are "POR," & both say they're almost out of them
(Get 'em while you can, they're not bad rifles at all!).
The fixed hi-caps, especially Chi-Com 20s are around, & they work well, but most of them have the big star stamped in (a little suspicious on a Russian, or Romanian).
You have to break the USA semi-detachable ones in, & it can be a real pain in the a$$, but once you get them to work they usually keep working OK.