This is a straw man argument. Nowhere did I say anything about anyone being called an engineer.

Doesn't context matter? If I went on a site mostly used by doctors to discuss medicine and posted my guide to doctoring french fries, wouldn't that sort of implicitly be saying I consider myself to be a doctor too? Wouldn't it either be offensive or a joke, if not an offensive joke?

No. Most human beings are aware of immediate context, and are more focused on mutual collaboration than nitpicking linguistics.

An "I doctored my fries" post on a medical discussion site would at best be a mild chuckle, and everybody would move on.

They'd especially move on if most of the people on the page weren't actual doctors, they just called themselves that.

Cool. What about a post called "getting better MRI results"? With helpful tips about how to adjust a machine they didn't understand and implying they were better equipped to read it than the people who understood both anatomy and how the machine worked? Would context matter then?

Hold on, let me answer that for you. They'd be called a jackass and laughed out of the room.