I have an extension ready for this, doing some finals tests these days. It calculates the numbers on the fly, meaning they are not stored in the database. Removing a post in the middle of a topic will shift all following post numbers. Personally I can live with this restriction, so other admins might too.
david63 wrote:Firstly you have to consider "soft deleted" posts
In my extension there's an option in the ACP settings to skip any non approved posts (i.e. not approved and soft-deleted posts) so that an admin can decide for himself which way makes more sense on his board.
david63 wrote:handle the numbering when a user views the posts in the reverse order
This is also taken care of. However, It requires an additional SQL query to fetch the number of non-approved posts on previous pages, provided skipping them is enabled.
It will also show the post numbers in the topic review when composing a reply as well as in the MCP topic review page. Furthermore, there's an option to switch to displaying post IDs instead of numbers.
The extension will be posted once 3.1.4-RC1 is out.