that does a request to the server for every comment listed, so you are basically loading up HN with a high multiple of the current number of requests per second if this becomes popular and / or gets loaded in threads with a large number of comments.
Not sure if this is a good idea.
The user profile page itself is only around 19KB....
I'm definitely not trying to DDoS Hacker News though. If this really causes problems I will delete the repo.
Anyway, it really isn't my call to make, I just figured I should warn you, in case you had not thought through the consequences of this becoming popular.
edit: unless I'm misreading your code it even does requests for users that are listed multiple times on a single page, you could easily save there by caching the results of your queries.
[1] http://diveintogreasemonkey.org/advanced/gm_getvalue.html
The very best way would be to ask for stuff like this to be configurable for those that want it but HN 'feature' requests are not usually honoured.