I repectfully disagree with this kind of reading of it.
If the speculation before you is correct, it would be like a DnD's paladin powers, ie you can do what you can do as long as you keep your oaths, it wouldn't be "you can, but actually you can't, lol".
There also would be a lot of situations (most, really) that would be in keeping with Valaya where we could actually use the rune without it being "if you do so you actually can't, lol". The examples given by the qm are major ones, as being in proximity of demons and warpstone are required to fight demons and things that use warpstone, and, as such, protection from involuntary poisoning is something that under no scenario would be frowned upon. It would go similarly for magic accidents, as long as the intentions aren't to create Dhar, as well as for handling violative materials. In a pinch, using Dhar as a necessity (say, using dispel undead) would probably be forgiven even in such a scenario as the one speculated by the person you quoted.
No, what actually would be punished, in such a situation, would be intentionally creating Dhar without good reason(remember, it pollutes) and/or using it to go full evil wizard without the usual consequences. It would be pretty much considered using the gift for evil, and I imagine that would be a pretty good reason for some smiting.