I see the excruciating pain of reading the same words that stick out. It's so excruciating that it's excruciating. Why would someone unintentionally excruciate someone with very lazy writing? It excruciates me so much when someone does that.

Hmm, yeah. The first one is repetition. I usually just google 'x synonym' with x being the word that due to the scene need to be repeated. And if the tone fit I'd simply use the synonym, otherwise I'd reword it.

For the second one, I kinda surprised that no people mention the two exception to this rule. First, when it's the name of a place like WI's light scintillation. Second, if it's fits the character background. Like for example if the character is a physic post-doc, obviously they'd use more esoteric vocabularies that does not reach the eyes of us mortal. Or if the character was meant to be an annoying know-it-all, or trying to impress other by looking 'smart'. For me as long it fits the scene, then that's fine.