Yeah, a lot of people see the terminology and shut down despite it only being place-holders for "the thing I explain to you". Duodenum sounds alien, but replacing it with "that thing right after your stomach" in every sentence gets tedious and unreadable pretty fast.

I fully agree that instead of all those "omg! that is not ELI5!" posts people throw around (some ignorant of the actual meaning, some not), they should just ask for clarifications. I really wish that was a rule, as in, telling people that something is not ELI5 instead of asking for clarification is forbidden. I've only very rarely seen such responses where I would consider it justified.

I had several instances where OP asked for an explanation that technically does break the rules. Something like "As an engineer, I learnt this and that math. But how does [complex mathematical theory] fit into my work?", where the only serious option is to explain based on OP's knowledge, not a layperson's.