Is it the humanoid quality of them? The animate inanimate theme?
They're definitely not furries, I know that much. But what exactly is special about them?

In a weird way I feel they're on the same level as pac-man, yet I still think they're somehow out of place

They're walking candy, aka inanimate food objects given humanoid features. They're generally considered not furry content, however they're also not human enough to be considered irrelevant. The site allows non-human humanoids and the like as well, so long as they have enough non-human qualities to pass (see: orcs, goblins, elves, demons, etc)

yeoldenut said:
In a weird way I feel they're on the same level as pac-man, yet I still think they're somehow out of place

Pretty sure many are feeling the same way. However we have chosen to go the road of making guidelines as objective as possible so that users are more clearly aware of what they can post here, rather than posts being deleted because staff member had gut feeling that it's not supposed to be here.

To me, anthro candy might be unusual, but not out of place. Look at it this way: e621 doesn't just cater to anthropomorphosized animals AKA the traditional furries, but also to most anthropomorphosized content in general, including anthro dice, food, plants, etc.

The mods have a hard enough time keeping human_only art off e6. It will be a while, if ever, before we can start making rules against not_furry stuff and focus on the site's mission of archiving quality furry art.

And along those same lines, living airplanes. D:

What qualifies m&m's as site related?

The delectable milk chocolate filling.