BuddyPress.org

always try and override the values if a filter is available instead of modifying the bp-core files (next bp update you’ll need to make the changes all over again)

bp_activity_latest_update() triggers the member-header activity – there is a filter bp_get_activity_latest_update

as for the forum # permalink – that is in the /groups/single/forum/topic.php theme file (can override with a child theme)