I seems that it works ok at my 2.3.3 forum (It is the 2.3.3 with the 2.3.4 Calendar.php file - that security fix).
I used this version of the hack
https://vborg.vbsupport.ru/showpost....4&postcount=48
EDITED :
Except one small bug (?).
A moderator can see other invisible users at the "Users Browsing this Forum" line, but not himself.
Overall great hack
If I encounter any probs I will report them.