Heres how one of my friends mirc looks (invision):
[10:51:15pm] 4[mynick4]13 shop

Their <nick> is [nick] (and colour coded), and so is their text.
if you used your example above, that formatting would be lost.
Having it processed internally by mircs swear filter would solve that problem. I dont see any way to avoid all this mess with a custom made remote script.

It could be avoided if the filter would be within a Theme System like my Message Extensions Addon offers it (even if it is not fully finished, but it works).

I added a feature called Content filter which will Replace incoming words. If i am finished it will give you the Choice to hide, Mask (****) or replace any word in the filter list.

You can find and try it here: http://mircscripts.defcon-one-script.de/tmp/msgext+.zip

The official Release v1.3 ( http://www.mirc.net/projects.php?go=1097394278 ) currently do not support that but i will update my Addon at mirc.net as soon as i think it is finished.

My mIRC Addons