Talkirc (atys)
... maybe a hot key that could allow it, since it's not the normal use of mouse in game, or when over the webig box a more os like mouse is used for that ingame window.
try using shift and/or ctrl in combination with the arrow keys while in writing mode.
I think ctrl + <- and ctrl + -> move the cursor and with shift + -> and shift + <- it selects the text in cursor direction letter by letter (or was it the other way around?)
hope that helps a little bit...
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