Highlighted topics can active as part of longer words.
For example in the main quest, Sul-Matuul is supposed to have the topic 'need' available after you get the ring moon-and-star. However, when telling you where to find said ring, he recites the following line:
"The eye of the needle lies in the teeth of the wind"
In which the 'need' in 'needle' becomes highlighted and allows you to bypass that entire quest.
Talk to Sul-Matuul about 'Third trial' in the attached save to trigger the bug (although I imagine this specific case only affects the English version).
(RM-2013 from redmine: created on 2014-10-13 by Alexander Bessman, , closed on 2014-10-22 by Miroslav Remák)