When is it best to use formal (bureaucratic) vs informal (conversational) language? When writing reports and documentation I prefer formal language, but for blogs I switch over to informal.
I've settled on a mix: plain language that expresses intent and the key points (not just using a thesaurus to replace jargon). And at the end, a hyper-detailed technical notes, methodology, and references section. The goal is any expert who's read the tech notes can read the report and understand the assumptions and math behind each statement.
Personally, I like this kind of reporting. Read the tech notes to check that it's reliable, then read the report with peace of mind. I was going to "translate" the jargon into basic concepts anyway, so this saves a step.