this post is about registering here, on forum.
In registration form there is a field “real name” and it says it’s optional, why when I don’t want to type my real name, I can’t register and there is an error message about this, that the name is required.
No. This was during registering using Google Account.
You can remove my account from here and I will try to register again and capture a screenshot this time
I know. But I also used another Discourse forum (not sure based on which version), and I could register without full name.
Discourse provides a setting for that actually, and I can confirm that this specific instance requires a full name to be provided.
Thanks for clarifying that it was via Google provider, probably a glitch in the Google oAuth module then, not taking into account that this field can be required if configured so.