The fee makes the market less liquid, and by a lot more than 2%. People offering trades going both ways trying to make a profit drives this together which means a better price for people who come to buy or sell. The fee, in addition to making a 2% spread the absolute minimum disincentive this behavior. The spread was at 15-20%, it's going to get a lot closer now.

There is another market, so if yo have a high spread and they don't you will always have the worst bid and asks.

An exchange site wants the spread down because that attracts customers. Once there is a thriving market is a better time to monetize with small fees or ads.

I donated. I think the site is coming along nicely.