Re: @thepseudo in the posts
If you are adding your own filters you can add them either in your theme’s function.php file or in bp-custom.php in your plugins folder.
This article introduces you to the concept of filters in WordPress (albeit from a plugin perspective): https://codex.wordpress.org/Plugin_API#Filters
To find the hook in question (content_save_pre), I suggest using your file editor and searching the files in your WordPress install. Also have a Google, and you’ll find some information: e.g. http://adambrown.info/p/wp_hooks/hook/content_save_pre?version=1.5.2&file=xmlrpc.php
[Edit: Rich has already given you the line to add for the filter – try it in your functions.php]
