No to almost everything except 'just for show' and 'only a few days'. Bad idea!

I know some who feel that the care of moss needing to stay damp...and then the care if the actual needs of the bonsai tree it can be stressful finding a balance. Most just use it for showing or if guests come over add it. Though...I know some who if the moss grows naturally they do leave it.

If moss is growing 'naturally' on a bonsai, there's something wrong with growing conditions to begin with. Sure, a particular tree whose north side on a cold, damp day may acquire a little moss, but it shouldn't be left there and encouraged as it's really not considered to be 'good' for either trees or bonsai as a tradition.

Please don't get me wrong, I'm all for trying all kinds of things with trees, plants, mason jars :-), and whatever else you like, but this forum's about bonsai and bonsai are not generally about tricks, though some well known, long proven-to-know-what-they're-doing experts, etc. can get away with stuff that's 'out there', but even those trees would not score high at all in traditional bonsai shows... so have fun, but don't necessarily call those creations 'bonsai'.