I'm the type that understands that humans are not perfect.
And human brains naturally are of different intelligent levels.
They sometimes make mistakes in their lives, and spelling/typing is one of them.
Most people can see through a typing or grammer error and figure out what the person is talking about.
And life goes on.
With that said, an occasional humorous "picking on" by someone over a silly typing mistake is a typical human trait, because as I said, no one's perfect.
It sometimes represents a playful fondness towards another person.
However, it also can be annoying, and sparking a defensive posture in the victim particularly if the "picker" has a reputation for being one of those "schoolyard bully types".
Being an online "grammer nazi" repeatedly is also annoying, and shows that the person has self-issues with others.
Now let's all move on and perhaps take a good dump, it'll make a person feel better.