posted a comment on a user's activity wall underneath a system generated message. could not delete activity-comment. this was possible in yester years. in vanilla 2.1 there is a delete comment anchor to the right of the time of comment, however this is not available on vanillaforums.org.
I haven't tested the changes you point to @Bleistivt but it may not fix the problem related to a user posting a comment under a system generated message on another person's activity wall. It looks like it may be overlooked.