[PLO10 SH] BB freeplay (quads)

It's PLO10, you have to shove.
Situations like this happen so so rarely that it's not actually worth it to spend time on looking for optimal lines. The only correct play involves you having a particular read on your opponents because some people will raise absolute garbage here, others will happily stack off with trip 6's and others will only have quads.

Why are people considering folding quads the last few days at micro plo i really don't know

In this situation, it could be super easy for villain to have A6xx... I mean, with 2 fours and 2 sixes on the board (and one in his hand one would presume), it will be very unlikely for you to have a hand that beats him; after all, having 64xx would be extremly unlikely, let alone having 44xx.

So to sum up to your questions;

1) He can definetly do this with A6xx
2) Tthis is NEVER a bluff for 99,9% of micro plo players. But he could be value raising a lot of 6xxx hands, especially A6xx or 6xxx with a flush draw
3) Like answered before, noone will bluff raise here imo... Especially once you pot twice on this board... Well some opponents may think this is a good idea, since it's hard for you to hit this board, but those are just huge fishes since you are potting into 4 people which just screams "monster"

I'd never fold this either, though it looks like quads, especially when he is so passive on the hand. IT could also be some 6x that waits to hit FH,so I'd stack off..