To ask about the specific case of "Show HN:" being removed from your
submission, the right place to do it is by emailing: hn@ycombinaor.com
I've never seen any official rules or guidelines regarding "Show HN:"
submissions, but there are differences in sorting between url-based
submissions and text-based submissions. Since text-based submissions
sink faster, I've seen some suggest using url-based submissions. On the
other hand, with a text-submission, you can specifically ask for what
you want (design help, content help, ...) and provide contact info.
From the following, it seems some changes may be afoot.
https://news.ycombinator.com/item?id=7761378
> We do intend to add a few things, such as a "show" link in the top
bar for Show HNs