The whole page is broken now. It works fine if done with TinyMCE buttons though.
You need to pick the allowed html tags that the users can use in your “functions.php”, like so:
function wp_bbpress_allow_tags(){
return array(
'span'=> array(
'class' => true,
'style' => true,
),
// add other tags to allow here
);
}
add_filter('bbp_kses_allowed_tags', 'wp_bbpress_allow_tags');
Keep in mind the tags you pick here are the only tags that will be allowed, so list all of them here.
Don’t ask me why the default allowed tags are different than the default shown TinyMCE buttons.