On that sub, their rules don't allow people who mostly post links to their own site. It's up to you if agree with their rule, but those are the rules they have chosen.
The common response is "if you don't like the rules make your own subreddit". Unfortunately that doesn't scale very well, especially if you're trying to replace a popular subreddit.
Of course the simple workaround here is that OP shouldn't be posting their own content anyway. The should send it to a friend who can post it if they think it's interesting.
Posting your own content if you aren't already an engaged member of the community is like walking into a room and shouting "hey everyone I have something you might like!". That's why there is leniency for active members of a subreddit to post their own things.
For people who are saying "thankfully HN is different!", it really isn't. It's basically the same as a subreddit run by the mods here. I personally like the way the mods run things here, which is why I participate here more. But at the end of the day it's just a different set of humans with a different set of rules (and a little bit more control since they can do things on the server that reddit mods can't). And on this "subreddit" they allow people to post their own content if it's relevant, similar to a lot of other subreddits that aren't /r/moviedetails.