I think that's a good point about the charge being in the similarities, running out the times we have wrongly perceived different things as being the same, even though Dennis put it the other way in the lecture Level 2 TROM:
So we are separating all the time, every time we are doing the command on Level 2, the “Difference” command, we're separating out all the time and we are running all the “similarities” simply to keep the flow balanced out, that's all.
Either way, it's plain that both similarities and differences need to be run.
On Level 2 I had mostly compared past people with present objects; trees worked well for this. I also tried bringing a recall of my late mother up against my wife in PT, this timebroke very quickly. For example, my mother was the taller of the two - I'd just never remarked that fact before, never having seen them together in life.
Timebreaking persons against objects seems reasonable considering that all we are timebreaking is their body, which is just another created effect. I don't think it's possible to timebreak the persons themselves (thetans) since they are causes, not effects. But I'm inclined now to try a Level 2 session in a busy place outdoors, as someone suggested on the mailing list, to see if anything more can be got from timebreaking persons against persons.