Looks like it was fixed way back when codebase was not modularized to this extent. Here is the ticket that was closed some 13 years back with commit that fixes it.
If you observe these check doesn’t exist anymore before updating last reply id and all.
// Update if reply is published
if ( bbp_is_reply_published( $reply_id ) )
update_post_meta( $topic_id, '_bbp_last_reply_id', (int) $reply_id );
Even I am facing this issue. Ideally they should not update reply count or any other metrics if the reply or topic is form. I have found a way to tweak the codebase and do it but I want the plugin developer to provide some hook for it.
HTTP status code received for the reference page is 404 and not 200. That will be considered bad for SEO as it is giving 404 response for page which has content to display. You can check the console also too see the status code
