Isn't it something... Stock PPS at over .90 when TD ameritrade noticed manipulation of rcch.
What it "isn't" is true. The TDA letter was written at a time when a number of brokerages were being attacked by hacker who broke into clients' accounts, sold their stock, and bought penny garbage in the hope of jacking the price up. The brokerages slapped on trading restrictions whenever they saw what they perceived as "unusual trading activity.
And that's all there is to it.
The whole thing is very well documented. You should do some DD.