I am confused on the subject of aliens interaction with motion tracking. How does one avoid being seen on MT.

Well most people will say walking will stop mt from picking you up - It doesn't.

Hit your move forward key twice and wait a second, then twice again etc.
Mt won't pick you up then.

Walking will work if you're cloaked/and or in the range of a sensory. I think that's where that rumor came from.

I don't even remember seeing a fix in a changelog for the bug where MT would pick you up if you moved your mouse when elevated above a marine.

Just take celerity and run at full pelt towards the marines. No confusion there.