Indeed. That's why HN is struggling with this problem, because HN chose to build its system around voting. So now it has to deal with one of the inevitable downsides of voting. Namely, that popularity is not necessarily indicative of quality.
"If you want to avoid this problem, what can you do apart from get rid of voting in the first place?"
Read through this thread. There are many suggestions.
"Without voting, what will be left of HN?"
Comments, articles, and community.
But I should note that I am not suggesting we get rid of voting.
"isn't that [a populartiy contest for comments] what we have right now?"
Yes. That's why I said your proposal was "just another way of staging a popularity contest for comments".
"I'm merely suggesting a way of improving it."
I'm not so sure it is an improvement as much as it is a different way of getting the same result, as it doesn't change the fundamental dynamic of the lack of quality in highly rated comments.
"This gives those who reduce their activity due to quality an equal voice rather than a lesser voice."
I suppose that's true. But why should less active users have as much of a voice as more active users? Would that necessarily lead to an improvement in comment quality?
To me it seems the only thing your suggestion would lead to is that popular users would become more popular, and the voices of less popular users would be drowned out even more than they are now.
"People shouldn't be writing solely to seek popularity."
But plenty of them are. That's part of the problem that having a karma score at all or rating/sorting comments based on votes at all. People will write to be more popular (which karma is a measure of).
Because users who don't upvote because there's nothing good to upvote are still active users.
If they're not active, why should HN assume otherwise?
If there really is nothing good to upvote, then I don't see what the adoption of the system you propose will do, as the extra proxy votes won't be used (there's nothing good to upvote, remember?).
The other major problem with your proposal is that it will be very open to gaming the system. Users could just create sockpuppet accounts to give their primary account the votes of the sockpuppet accounts.
Of course, even with the present system users can create sockpuppet accounts. But at least with the present system, voting from the sockpuppet accounts has to be done manually rather than automatically being aggregated in to one account by HN itself.