[GordonS]

From the guidelines:

"Blog posts, sign-up pages, and fundraisers can't be tried out, so they can't be Show HNs"

The only way to try out your service is to hand over card details.

[LarkaUZ_]

Well this is a paid service... This is not a sign up page onlt. If we follow your logic any service that require card details can't be submitted to HN.

[grzm]

The distinction is they aren't appropriate for "Show HN". They may be submitted as normal submissions.