By obscurity, I refer to the specificity of the mechanic and the degree of investigation needed to properly resolve the question. I'm counting cases in my memory where someone refers to an obscure interaction between mechanics where I think 'wait, does it really work like that?' and check LoL wiki. I can't give specific examples of mechanics the wiki got wrong off the top of my head, but the questions were on the order of 'Does Cleanse remove the damage reduction portion of Exhaust?' or 'Does Tibbers' DoT apply immediately upon cast or delay a second?' or 'Can Malphite be CC'd out of Unstoppable Force?', as opposed to questions like 'What does Morgana's ult do?' or 'When was the last time they buffed Ezreal?'.
As it turns out, LoL Wiki appears to be wrong about Malphite's Unstoppable Force, stating that it can only be stopped by lethal damage when a lot of posters seem to be getting CC'd out of it by e.g. Shen taunt. So, y'know, one out of three right there.
All in all, Eld's estimation of the wiki's accuracy would seem to be, well, accurate.