I MM a lot of trades, and I don't do it for itrade, or rep of any kind.
Honestly, I don't give a shit about rep. I have done probably 5 times as many trades on this site than my itrader shows. I just really don't care.
But I think that if the situation arises, its' perfectly fine to leave a MM rep.
They are the ones doing and helping out with the trade. They are just as involved in the process as the people trading.
And for that reason, I think it would be perfectly justifiable to leave a MM trade rep.