Before Empires it was more a 'if I trust you, fine, just not too tight', because the scars from the vex often hurt, and sometimes there was mild paranoia of thinking they're about to hurt him mid-hug.
After Empires, it became a no-go. In fact, most physical contact became a no-go, because now he's got more scars, and anything moving on his skin reminds him of sculk. Especially if he can't see it, it's constricting, and/or if it's something cold or slimy, So hugs, something he can't see, tight around his torso? Absolutely not.
And he knows it's irrational, and hates himself for it, but he can't help it. It's the same reason he will not, under any circumstances, walk through dense mangrove forest.
However, he does have a few exceptions:
-Cub is also perfectly giving hugs to the hermits, as long as they don't hug back,
-Scar is allowed to hug him, because he knows how to do it gently, and Cub trusts him 100%. Also Scar gives amazing hugs, and he loves hugging Cub especially, so who is he to deny that joy to his best friend? Surprise hugs are still off the cards, though, and Scar always asks before hugging from behind.
-He's becoming alright with being hugged by Cleo and Joe. Also Ren sometimes, because Ren is a huge hugger, and they've been good friends since Kingdomcraft
-Skizz may also be joining the list as well, currently only if Scar's around for emotional support, because gosh dang it his hugs are just that good.
-If another hermit is deeply distressed, desperately needs a hug, and there's no one else around, he will allow them to hug him.
The hermits are completely understanding of his boundaries, and happily listen to and obey them. Plus, if he ends up hugging hermits he doesn't usually hug, Scar gives him a cookie for his bravery.
We stan respecting boundaries!