Re: comment activity record
The function bp_activity_record will be deprecated in BP v1.1. In its place, a new function has been created: bp_activity_add().
Before you spend time coding a plugin that will not work with v1.1, I suggest visiting Trac and seeing how the new function works. In fact, there has been quite an extensive re-write of the activity stream codebase, so there could be a number of changes that you need to bone up on.