I’m currently using the WYSIWYG editor TinyMCE with bbPress for a project. Unfortunately, bbPress doesn’t like it when it gets <p> tags through TinyMCE and therefore messes up the post. I have written an (extremely) simple plugin for TinyMCE which transforms <p>s into double linebreaks before posting therefore preserving compatibility. <br />s are transformed into single linebreaks.
The plugin is based on the BBCode plugin by Moxiecode Systems AB distributed together with TinyMCE, so they deserve most of the credit. I only adjusted a few replacement calls.
Currently there is one disadvantage: When you want to edit an existing post, double linebreaks are not converted back into <p>s, but into double <br />s. This usually looks just fine, but is not perfect.
Unpack the zip file into the TinyMCE plugins folder. Add “bbpress” to the list of activated plugins.
Important: Also set remove_linebreaks to false, or all linebreaks will get removed by TinyMCE.