You just need a mechanism to weed out troll behavior. Maybe a few moderator users. As researchgate shows you don't want to use real names; people will not give honest feedback. Dont forget science has a lot of politics. Besides, anonymity works well with journal peer reviews, why change that?
I think it's fairly easy to give honest feedback about a paper you dislike without it being politically disastrous, just something along the lines of: "Is there a reason why you used method a instead of method b?"
It hasn't been long enough to see how these specific groups would act with anonymity, and certainly some groups are more resistant to trolling than others, but I think in general anonymity will tend toward the nasty part of the spectrum.
Even in public, recorded lectures, I've seen full professors just go to town on the speaker trashing their work, especially if the work is controversial in any way. It's nice to be able to see who's acting that way.
A friend of mine had a paper response written to his first ever paper that point-by-point tried to discredit his whole point. Then his professor had to step in and write a point by point rebuttal, because someone with just one paper has no clout to deal with that really. It's nice to see that happen in public because now the guy just looks like an ass for jumping on first year PhD students.
