Hi,
We will investigate tomorrow in depth this issue ( [DOM] Found x elements with non-unique id ).
The second thing related to the replying to the comments it may be caused by the paginatiation tiat is no ajax, it’s directly via url
You will click reply or comment on our demo you will see it works, also if you press load more a new content will be pulled in the same page without refresh https://seventhqueen.com/demo/sweetdatewp/activity/
We have also those errors in console related to [DOM] Found x elements with non-unique id and the functionality isn’t affected at all.
On your install if you press Load more at the bottom of activity page will open this link https://khiadmin.staging.wpengine.com/activity/?acpage=2 instead of pulling new content there.
If you had child theme and other plugins that can interfere with buddypress de-activate all except buddypress and see if it works as it should.
Let me know if it works to comment/reply with all plugins except Buddypress and child theme off
Cheers
R
