We have a simple list of bbcodes that we are trying to support like @Ghan explained because we are a 20 million + board. We are by no means a small community and this was not an easy decision that we came to, but we have determined that Discourse is the best software for us moving forward. We’ve gotten the import ironed out, the only thing that is stopping us from migrating is just figuring out this last step. Now I can be convinced to drop tables since we want to drop any BBCode that Discourse or Markdown fully supports. However, Tables was one that couldn’t just be easily rebaked into the markdown version because replacing table td tr and so forth into the correct Markdown Syntax is not easy or rather nigh impossible as far as I can tell. So dropping it is fine, even if it can’t be rebaked easily but just learning how to do it, will most likely help us figure out everything else.
We were able to drop [h1] as an example because that one is indeed simple to alter since all the H tags just need to become the equivalent number of #.
We have an entire list at: Tutorial - RpNation - BBcode Guide | RpNation and a few more besides the ones in this thread, have already been dropped because they were super simple to find/replace into the markdown equivalent.