Can someone explain the logic of underbidding swap demands?   i.e. placing your swap demand at 0.0999 or one penny bellow that at 0.0998. It's as if you're artificially keeping the demand high while don't really want your demand to be filled  

It makes sense for offers where they're underbidding each other, but if anything i'd expect demands to up each other by a penny and placing demands at 1.0001