Did you have many trades that look the same or trades for the same purpose... Becasue that is not allowd, if you didn't do that then I don't know...

Donating is done out of appreciation, it does not give you any additional rights.
If you wanted to correctly "represent" your trade, you should have searched "weapon" for the trade slot, and selected normal weapon. That covers all regular weapons easily.

One of my trades was closed for the same reason (I guess someone got jealous and reported it). I used one big single trade to list all the items I'm selling and an untradable item to represent it. Then I would just link to that trade in every other one I had (so people could see my other items if they were interested in them).

Personally I don't think it hurt anyone but then I read it's against the rules. I mean you can't trade that item anyway so why is it even the list of items you can sell? If you could disable autobumping on trades you couldn't even say it clogs the main page. Yet I keep seeing people selling 7 stuff and a Gold/Silver/Bronze Badge or whatever.

I think this rule is unnecessary, either that or a blacklist of items should be made that aren't included among the other items.