I think you’re on the wrong way to prevent spam posts. This is not a solution. Spammers copy their spam texts and paste in editors. It doesn’t matter the editor is a rich editor or a plan text. wpForo has built-in Antispam system which may help you a lot.
1. It sets new registered users’ posts unapproved. In this status posts are not visible for others until forum admin make it approved. This works based on wpForo Antispam functions. It also integrated with Akismet. You can install it as well.
2. wpForo doesn’t allow new registered users to attach files or insert links in posts. You can manage the level of new registered users based on number of posts in Dashboard > Forums > Tools > Antispam admin page.
3. In Dashboard > Forums > Tools admin page you can find built-in reCAPTCHA API. I recommend configure and enable wpForo reCAPTCHA for all forms. Before testing that, make sure it’s enabled for all forms:
