List of steps to reproduce (step by step, including full links if applicable):

1. Download and place the file(s) in a directory called Comments in your extensions/ folder.
2. Add the following code at the bottom of your LocalSettings.php:

wfLoadExtension( 'Comments' );

1. Run the update script through SSH which will automatically create the necessary database tables that this extension needs.
2. Get the following result in SSH (amongst other things):

...Comments table does not contain Comment_user_id field.
...Comments table does not contain Comment_Username field.
...wiki_user_id key doesn't exist.
...wiki_user_name key doesn't exist.
...Comments_block table does not contain cb_user_id field.
...Comments_block table does not contain cb_user_name field.
...Comments_block table does not contain cb_user_id_blocked field.
...Comments_block table does not contain cb_user_name_blocked field.
...cb_user_id key doesn't exist.
...Comments_Vote table does not contain Comment_Vote_user_id field.
...Comments_Vote_user_id_index key doesn't exist.
...Comments_Vote table does not contain Comment_Vote_Username field.
...Comment_Vote_user_id key doesn't exist.

What happens?:
It looks like the extension is installed. I can post a comment, but the above fields remain empty in the database.

What should have happened instead?:
I assume the above fields should not be registered as they were above.

Software version (if not a Wikimedia wiki), browser information, screenshots, other information, etc:
*Putty

This has been registered in April 2020 already on the talk page of the extension.