It
is expressly discouraged, it's just an entirely subjective thing:
"On-Topic: Anything that good hackers would find interesting. That includes more than hacking and startups. If you had to reduce it to a sentence, the answer might be: anything that gratifies one's intellectual curiosity."
I have been watching the HN new queue turn into an "all tech news" feed, at some point it becomes a true firehose and there is not a chance at all of finding anything "thoughtfully submitted."
PG doesn't seem to have an issue with this: http://news.ycombinator.com/item?id=475779