[woofcat]

The only real selling point is it allows you to distinguish users apart from one another really quickly in a threaded conversation.

Sometimes someone other than the original commentator replies and unless you're paying attention to the user names you may make a presumption based on assuming they're the same person.

[kaitai]

I kind of like that on HN I read through without necessarily paying attention to who is who. I focus on the comment or discussion rather than the personalities, and if I want to argue with a person rather than a point I have to go back & look at which comments are theirs.

[hiccuphippo]

It could be simpler to use a different color for their name, like with new users having a green color: When a user comments more than once in the same subtree, change the username color in all their comments. Leave single commenters as grey.

This should be pretty easy to do with a greasemonkey script.

[SmellyGeekBoy]

The unofficial HN mobile app "Materialistic" does something similar to this.