Comment appended to cvar value
When a cvar in an exec'd config file is immediately followed by a comment, the comment (up to the first space in the comment) is appended to the cvar value.
set sv_foo 123//my comment
sv_foo is "123//my" ["123//my"] comment
If it's the first time the cvar is being set, the part of the comment after the space is set as the cvar's description.