You noticed too... Some of the screen names have been dormant for months, and all of a sudden they become active on the TM just as some of the the other, well known names disappear. And then there are the screen names created in the last few days, but even though they are newbies, they know the lingo and write with a familiar style and as if they have been posting here for months.
I've been noticing the same thing you have. Especially the ones that are brand new but know the lingo and the inside jokes... interesting.
Yup! We know who they are, even thought they think we think they are someone else.