Commenting on posts:
When posting comments you can log in using one of the services that pops up when you click on the “leave a comment” link.
Basic manners are a big deal, which is the reason you will need to sign in to an online service before you can post comments. Anonymity seems to encourage some people to behave in ways they would never contemplate if we met in person. Do not ever comment in any way that is insulting, vulgar, or defamatory, particularly when responding to another’s comments. If you like that sort of thing you are more than welcome to go post on Reddit.
By all means disagree, but let’s agree to disagree agreeably.
If you don’t want to use a linked service you can create a WordPress Account. No need to create write a blog — you only need to sign up for a user name.