I agree with the suggestion that submissions should be disallowed until one reaches a specific karma value. It is becoming incredibly harder now to up-vote the right kind of posts from the 'new' section. A smaller sample space would be helpful in getting mostly the right content on the front page.
Writing thoughtful comments (even if they are disagreements) to get the desired karma for submissions is as good as a pseudo-invite.
The one tricky part would be whether to allow 'Ask HN' posts or not from new accounts that haven't reached the specific karma level yet. I think they should be allowed, as sometimes one needs to create a temp account, to get some useful feedback/suggestions for some situations where one cannot disclose the identity very obviously.
Writing thoughtful comments (even if they are disagreements) to get the desired karma for submissions is as good as a pseudo-invite.
The one tricky part would be whether to allow 'Ask HN' posts or not from new accounts that haven't reached the specific karma level yet. I think they should be allowed, as sometimes one needs to create a temp account, to get some useful feedback/suggestions for some situations where one cannot disclose the identity very obviously.