Here's the cure; SpamMeNot.
http://wow.curse.com/downloads/details/7477/
SpamMeNot is an AddOn that can filter out text on many levels, filter out Trade Channel spam, auto-ignore and auto-report, and much more. I use it myself to avoid goldselling spam.
If you're going to use it, I recommend setting it to this configuration to avoid blocking out everything;
_______________________________________________
Level Block
[list]
[*]Filter Invites - Checked[/*:m]
[*]Inform - Unchecked[/*:m]
[*]Level - 3-5[/*:m][/list:u]
Spam
[list]
[*]Alert - Unchecked[/*:m]
[*]Auto Report - Unchecked[/*:m]
[*]Trade Channel - Unchecked[/*:m][/list:u]
_______________________________________________
So what does this do? Well, with this AddOn set on these configurations, you've basically shut the goldsellers out. All characters up to the level you set just ceased to be, at least you won't receive any messages from then, no whispers, no says, no yells, nothing. Also, the people who you have blocked out will not be made aware of this, they won't clog up your ignore list or anything of the likes.
It's paradise!
:blaugh: