Re: Disable the ‘REPLY’ function to already existing post reply
If you use BP 1.2.8, go to bp-activity/bp-activity-templatetags.php
at line 647 is function bp_activity_recurse_comments
with a if statement if ( is_user_logged_in() )
in which is the word “reply”
rewrite this function to retrieve the word and put it in the functions.php file of your theme
This is a solution, but probably they are others 
