I think it depends on the reader. For me it’s important to look up every word I’m unfamiliar with – but then, I’m not spoken-word fluent by any means, I can only just read and translate most things in the two languages I know a bit of into English given a dictionary, paper and pencil, and enough time. I never got to a point where I could possibly read without also doing a written translation, so it never broke my concentration to look stuff up. I bet you work with more advanced language students than me, but I dont think it would disturb me too much to look up words. I do something similar when I read translated philosophy texts that have oodles of language-related footnotes, like this, and though it can lead my mind off on a tangent sometimes, I find that more often it helps overall comprehension of the sentence.