Hi, I have the same issue.
I want only Admin to be able to post new updates.
Subscribers can only post comments.
I am not using groups.
I have tried your solutions above, but you’re not clear on exactly where to upload the file to.
Btw – I can only find /wp-content/plugins/buddypress/bp-activity/actions/post.php
Then I’m not sure if I should rebuild the folder structure in the child theme, or just put it in the root folder.
Or if I should add your code at the bottom or overwrite the existing code.
Your help will be invaluable.