Changing screen name
Maybe it isn't a bug, but it can be annoying to some users.
By default both my username and screen name were: milot.shala, while I was typing to change my screen name to Milot Shala, textbox changed the text to milot.shala automatically, assuming that I was going to type milot.shala.
How I changed it?
I typed milot.shala and replaced the . (dot) sign with the space, changed the M and S to capital letters from my first name and last name.
I am using Google Chrome on Linux.
I'm thinking this was the browser "helping" you, we have no automation going on for that field.
You are right, it can be a browser helping me as long as you don't have automation on that text field :D