So, when a Reddit user asked, "What's your 'Oh...you're not joking' moment?" people were ready to share the story of an awkward, misunderstood, but completely serious interaction. Note to self: don't be the first to respond in the wedding group chat.
I’m a geophysicist and was working at the time for a major oil company. I was paired up with a colleague who is a geologist. One time we were taking a lunch break and chatting about our project when another one of our coworkers, a drilling engineer, sits down at our table and starts to talk to us about the flat earth theory.
I thought he was joking around at first so I snort laughed. Turned out he was dead serious about trying to convince a geophysicist and a geologist that the earth was flat. We both lost all respect for this idiot that day. - Witty_Goose_7724