Dakuten(what you call “dots over letters”) are used to modify the way consonants are pronounced, not for emphasis, e.g to turn the character for “Ka”(カ) into “Ga”(ガ).

And the usage of katakana in the way the parent describes isn’t “tiring.” It follows almost the exact same pattern as words are italicized in English, where a word or phrase is represented differently from the surrounding text. Less common/standardized, but not tiring.

EDIT:

My bad on the bouten/dakuten confusion. Apologies.