This might be true internally and initially, before any ant-spam, anti-upvote-ring detection takes place. Effectively, from a user point of view it is not - at least for me.
When I look at the points one of my submissions get and compare my increase in overall karma it is very roughly 50% most of the time. Needless to say that I never participated in things that would be considered unethically (voting-ring etc.). Also not a complaint at all, just an observation that goes against what is often written in "about HN" type posts (but not OP).
EDIT:
1. My observation is from more than a year ago, so things might well have changed.
2. As lordnacho points out below this seems to be true only for stories. Regardless why it happens, awarding stories with less points than comments makes a lot of sense to me. After all posting a suitable story is much less effort than writing a decent comment.
Both modulo moderation, of course.
Occasionally, though, I have this post that gets a decent amount of upvotes but not a single comment. I never understood why. I post for the comments and not for the upvotes. It is very frustrating, especially since it is a miracle to me what distinguishes these posts from the popular ones.
Capping the points on these makes a lot of sense though. In the end they don't contribute much.
https://meta.wikimedia.org/wiki/Cunningham%27s_Law
>Cunningham's Law states "the best way to get the right answer on the internet is not to ask a question; it's to post the wrong answer."