alt Hacker NewsCore function of HN Front page is based on "other people filtering stuff for others". Filtering out by any criteria (karma, account color, first letter of the nickname, whatever) doesn't automatically mean that someone is a jerk as you have stated in the comments nearby. It just means that someone is selecting the information to consume and does not harm anyone (perhaps besides the selective person who might miss interesting info due to selection).
The filtering is supposed to be based on the quality of the content, and it's only useful to the extent that people filter either on quality directly or closely correlated metrics.
If everyone votes purely on basis of the first letter of the username, to use your example, then the votes provide no useful information and you may as well abolish it.