Sharepoint comment permissions by users

Yes, it is possible,

Manage permissions at the page level or library level. Here's how:

Page Level Permissions:
Go to the SharePoint page where you want to restrict comments.
Click the gear icon (Settings) and select "Page permissions."
Identify the specific user account you want to restrict.
Change their permission level to "Read" or a custom permission level that does not include the right to add comments.

Library Level Permissions:
If comments are enabled on documents within a library, you can manage permissions at the library level.
Go to the library.
Click the gear icon (Settings) and select "Library settings."
Under "Permissions for this document library," you can manage user permissions similarly to page permissions.