ToME: the Tales of Maj'Eyal

You can unlearn lower tiers of talent trees while keeping higher.

Learn talent 3 and 4 of a tree.
Accept to close the window.
Open it again, unlearn talent 3.
Accept.
???
Profit!

Would someone be able to tell me what the reasoning behind the prerequisite skills are? Beyond things like the Cursed Aura tree (adding dark gifts to cursed items would be almost completely useless without being able to curse items), is there a reason that often unrelated talents are required for higher-tier ones?

I ask because while being able to unassign prerequisite skills may be a bug, it also might be worth revisiting why we have prerequisite skills in the first place.

Forcing you to commit points in a "weaker" skill in order to place points into that "omfg" skill?

Makes sense to me.

I'm sorry to say that it looks like it's been fixed in svn. I had hoped that someone would be able to point out one or more good reasons for the tier requirements on the skills, but a quick search seemed to point to a lot of people willing to do away with them, or at least redesign that requirement.