Select a segment of text with your cursor, keeping your finger on the left-mouse button drag your mouse down to the editbox, right click, and then let go of both buttons.

The text should still be selected, the text will only reappear as normal when you move your mouse somewhere back into the channel window.

:shrug:

Confirmed, looks like a small glitch

6.12 - Can't resproduce
WinXP

I was able to reproduce it here, 6.12, WinME

/me confirms, too.
v6.12 on Win98SE

Confirmed. mIRC 6.12 WinXP

nvm, I got it-- Didn't work for a large sum of text, atleast how i tried it.

I doubt it's a feature, since it's not documented (I've never seen an undocumented key combination).

If you've got a scrollwheel on your mouse, do this and then scroll, funny++