Post number on slider disagrees with post

[Mittineague]

At SitePoint we do it mainly for different reasons, but it is easy to display the post id number near posts:

Show post numbers

It is hard to say if this is what you are looking for, but it should get you close. https://github.com/sitepoint/discourse-theme/blob/b4b4a7218ffbbfd4ee3cf8aa7421d29c96fdc4ed/assets/stylesheets/desktop/topic-post.scss#L45-L51 We use that CSS to put #1, #2, et al on a topic after the date/timestamp.