There are 2 main ways investors can hold shares in Computershare. One is DIRECT STOCK PLAN, and the other is in BOOK.
The Heat Lamp theory suggest shares held in DIRECT STOCK PLAN allow the DTC to manipulate shares and price. Also, even having just 1 fraction of a share allows for ALL the shares in the account to be compromised or used for ill intent. The concensus is to sell all fractional shares and convert all Direct Stock Plan type shares to BOOK only.
Original post [here] (original post seems to have been removed)
The Heat Lamp Theory original writeup can be accessed in the Superstonk Library of DD [here]