Removing comment box on single event page in modern calendar event can be done by following this visual instruction.
This is a default feature of WordPress. But if you want to remove the comment box on one or all of the events, do this:
A:

OR B:
#1:

#2:

#3: Update (save).
If the previously mentioned methods did not solve the issue, you have the option to hide the comment box by utilizing CSS codes. Simply insert the following code into MEC Settings > Custom CSS.
.single-mec-events #comments {
display: none;
}
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