As you can see in my screenshot (https://snipboard.io/o4GdFs.jpg) comments are available to Rookie theme. In the demos you are mentioned, probably are disabled from the Settings to avoid spamming.
1. Go to SportsPress->Settings->Matches->Event Options and tick the “Allow people to post comments on new articles” option.
2. Go to a match edit page and confirm that the comments are enabled.