One such benefit is that posts from the same person, even under different names, are linked together under the "Details" of that person. People don't realize this. And this makes efforts from someone creating multiple personalities to agree with himself easier to spot.
I spotted the following in a comment thread on a post at the Seforim blog, discussing Friedman and Heilman's recent books about the Rebbe, and the interchange between those authors and Chaim Rapoport.
There was one commenter named Nachum, who was in favor of the authors of the book. And then, the following comments appeared:
So, was "nachum" trying to misappropriate the true Nachum's name, as was alleged by DF? I would say absolutely. Why do I think this? (BTW, I will use lowercase nachum for the impostor and Proper Case Nachum for the original.)
Well, looking at "View details" for this "nachum", we discover all his posts, by account or IP address. And so, we discover that "Guest", immediately below nachum, congratulating him (the regular Nachum) for seeing the light is no other than "nachum" himself!
That is, nachum posted this and then pretended to believe that this was the original, regular poster Nachum. He was thus trying to foster this misunderstanding.
DF, a different person, informed Guest that this was not the same as the regular commenter Nachum; noted that it was transparent that two or three dedicated Chabad posters have been posting under multiple names, that this was transparent, and bad; but that it was worse to pretend to be regular commenters.
Lol!, who agrees that it is not regular Nachum, though thinks that this nachum is in the right, also posted under several different pseudonyms.
"Guest" then asks DF why he accuses bloggers of posing. All in innocence. But this is the same "nachum" and "Guest" as before. And indeed, he was posing, and trying to convince others that he was true Nachum, by first posting as nachum and then congratulating nachum for changing his mind.
Then, Shaya R says he doesn't know whether this is real Nachum or a different nachum, but he agrees. But Shaya R = nachum = Guest.
Earlier, this same commenter, going by the name "Menny", was arguing with Nachum. And repeatedly, under other names, referred people to read Menny's remarks.
I understand why he would do this. After all, he thinks he is right, and that the ones he is arguing with are in the wrong. Even so, it is not arguing fairly. It produces a false sense of consensus with his own opinion. This is dishonesty.
It is great that the Halo commenting system lets us spot this, so long as those who abuse it are not aware. (The first time it is pointed out, they will likely take awkward steps to avoid the revelation of their dishonesty.)
But it is something to keep in mind on other blogs, where all you need to put in is a pseudonym. You might be arguing with the same person, despite five people arguing with you.