Some high-karma member could quantify this by posting half their comments from a new account and A/B testing.

As it happens, my wife is a HN member but has not found it easy to get traction for stories she submits. On a couple of occasions I have re-submitted an article that I thought was unfairly overlooked and it has attracted replies and karma in abundance. Anecdata to be sure, but based on this and other observations in HN and other online communities I think your hunch is likely correct.

If anyone feels like exploring this in R or somesuch, MetaFilter (where upvotes by other members are public) makes a large amount of its user pattern data available for analysis: http://stuff.metafilter.com/infodump/