Okay so I just got the Mercurial Demo Suit. After equipping it, I hover over the loadout summary at the bottom left and it shows that the movement speed increase that the suit gives is a negative bonus. I'm not sure if this is a bug or what but to me, I think movement speed is more of a positive bonus.
http://cloud.steampowered.com/ugc/955012050944874430/617860B984B0306DA2B...
old bug
hasn't been fixed in over a year