To learn how to show/hide WordPress comments section, please go to a blog post editing(or add new) page.
Activate/Deactivate the comment here(“Allow Comments”) at the right sidebar:
If there isn’t the Discussion options on the sidebar, please click the 3 dots icon at the right-top corner, click Preferences at the bottom of the setting panel.
Activate Discussion, the Discussion options will display on the sidebar.
Set Default for New Posts
If you want the “Allow Comments” is unchecked for all new posts by default, please go to “Settings > Discussion”, uncheck the “Allow people to post comments on new articles ” option: