As far as I know, even some ancient boards had HTML filters years ago.
They allow some basic html to be posted, all else gets converted into plain text.
Obviously, we cannot allow javascript to open infinite windows and other funny things. Even funny background pictures and colors can be a pain and probably should not be allowed. Nor should closing html tags, unbalanced h1 tags, etc. So the way html is implemented, without filters, it is totally unusable. It MUST be turned off!!
I did a search on the board, and it is the unanimous opinion that html MUST be turned off for safety reasons.
Why would our visitors, most of whom know some rudimentary html, have to learn markup? We are not that important to them, that they will learn a new language. this is like requiring them to post in Russian!!!! Our users are up in arms since I cut html posting!
I don't think it is necessary to reinvent the wheel. I believe html filters can be copied from other boards, from chats, etc.
For starters, img, h1,h2, a href, and tables will do. Real fancy html is not needed.