r/macapps says "Be sure to double-check that your app hasn't already been submitted before you submit it!"

Sharing your stuff is fine, only being active posting your links risks being considered spam. Many subreddits also have automatic systems that hide suspect content for a mod to check, which can be quite aggressive.

I THINK reddit-global anti-spam deletes your account, so it's probably just the individual subreddit blocking your newest submission. Their sidebar even says that they have a spam filter.