would it or would it not be allowed for multiple people to participate in a 180 run? im thinking about doing a run and maybe switching off with my brother for certain levels. of course both of us were to be credited.

Not under the current ruleset, as 180 Emblems is not a co-op category.

And I don't foresee it being one either, if it's just too long for either of you to do alone, then that's how it is.

You could do it anyway. You just wouldn't be able to submit. It would be fun to watch at least.

Honestly a 180 relay race sounds like a fun Idea TBH. Not for the leaderboards here, but as some kind of event we occasionally do.