Common grammar mistake

[ataru]

Hey guys,
On pretty much every forum I've seen, somewhere upon logging in something reads:  "Hey, {username}, you have x messages, x are new."

Does anyone spot the unnecessary comma after "hey"?   

Well, this is definitely not a serious bug... just one of those little things I have to point out.  It should probably be fixed on a later release of SMF.   

[Oldiesmann]

I don't see any problem with that comma there. How is that bad grammar?

[Thantos]

In that particular case the comma after hey can be there or not.  It changes the meaning somewhat but both versions would be fine.

"Hey you have x messages, y are new." and "You have x messages, y are new." are both correct.  It is just a matter of what you are inserting into the sentence.

[karlbenson]

Ahh This this reminds me of my English Language days.

As far as I'm aware in English that first comma would make the {username} and second comma redundant as it wouldn't be valid.
It can be
Hey, you have 2 messages ....
Hey you have 2 messages ....
Hey dude, you have 2 messages
Hey {username}, you have 2 messages
but not
Hey, {username}, you have to messages

That would go for whether your using hey as a greeting or hello (eng/(int)eng/US english) or hullo (english).
With the username/person its modifying the greeting and so must be together or left out.

Also technically speaking the last part of the sentence is valid.
"[...]you have x messages, x are new."

But the taught/preferred way would be to put the focus on the important part by having it at the beginning.
(eg informing the user of their NEW messages BEFORE stating the total amount.