Tested on: mIRC 6.16

1. Set your highlight on "star"
2. If someone says "star"-something everything is fine,
i.e.
<Ninja> what a starry nite
(highlight doesn't trigger)
3. If someone says "star" followed by an ASCII extended charater, the highligh triggers
i.e.
<Ninja> starò
(highlight does trigger)

According to the help highlights should trigger only on full world matches if you don't use a wildcard, so it's not working properly.

Please note that this bug does not trigger in case the highlight trigger is followed by regular characters and not directly by an ASCII extended character.
i.e.
<Ninja> stareò
Does not trigger the highlight
<Ninja> starò
Does trigger the highlight

I hope it helps.

--
Ninja