Show HN is for something you've made that people can play with. Landing pages, email signups, and fundraisers aren't things people can play with, so we edit "Show HN" out in those cases.

For example, instead of an email signup, Show HN is for the thing you email people about once it's ready; instead of a fundraiser, Show HN is for what you build with the funds you raise; and so on.

We're planning to feature Show HNs on the site a lot more, since most people agree they're one of the best things here.