trader412
I'll try to answer you day trade questions. It's been a while so the brain may have some rust on it.
Lets tackle the form T question first.
These type of trade letters are used on some exchanges and not on others. Some exchanges have different meanings.
I'm not sure if there is one place to read about what letter fits what meaning or what exchnage uses what letter. So you may have to research each and compair.
As example years ago the form t was just used for institutional trade made after hours so their large buys or sells wouldn't effect the normal flow of the market.
Since the major increase in ETCs hedge funds have become large block traders also and the electronic platform speed has basically change brokers fee structures, lowering the cost for each trade.
Thus, large block orders can be broken into smaller orders, allowing stealt with out order protection by floor traders and the like.
It has been my understanding trades reported after hours with a form T still indicates a single private client protected trade. And brokers or floor traders will accumulate during the day (personal inventory) to close the client AH.
What exchanges use this or weather institutions & hedgefunds or just big guy private investors, still do this, I'm not sure. But you still see form T on the NAZ OTC market.
My guess has been institutions & hedgefunds don't trade OTC much. And before form T meant those traders.
Thus my rule of thumb has been, form T big guys, no form T M&M daily share swap book settles. I may be wrong, and IMO it would be hard to track down what exchange & what group still uses From T as a type of trade.
I've only seen it on the OTC, but haven't really checked anywhere else. Becasue I'm not concerned with market manipulation on larger exchanges.
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As for M&Ms holding back retail's desire to improve a stocks price. What you mention with HDSM MM is known as a CAP or CAPPING the stock move. It happens all the time.
WHY could be many many darkside reasons, and I have trouble thinking on the darkside correctly. So when I see it, I just move out when possible and find another play.
I've grown very tired of the stress & effort it takes to trade a highly manupulated penny. Personally, I like to relax while making money and there are just too many trades coming around every day to stress over one penny, event if you like it. IMO
http://www.investorshub.com/boards/board.asp?board_id=3972 Welcome to my mind! 
