What does W stand for?

I get email from Literotica readers every now and then and had this today:

This message contains feedback for: SirSinn
About the submission: Day by Day
This feedback was sent by: Anonymous

Comments:

W

*DO NOT hit the REPLY button to respond to this email.*

And that's it!

W?

Wow?

WTF?

Wanker?

What??????

Should be making a start on next chapter of Family Business this weekend.