1. The interviewer is half your age and has a quarter your experience.
2. He has no training in interviewing, and runs you through the same whiteboard horseshit that he was put through as a very junior developer..
3. He sniffs and fidgets and if you agree to code on the whiteboard (I won't) he makes misleading suggestions.
4. He doesn't care about stability but constantly suggests that you should think of ways to make it run "a little faster." He's a compulsive.
5. He constantly steals glances at this own monitor because he's way behind on his own work and wants to get back to it.
6. You can see from across the room that his code is all flush left, so he's using mid-function returns. He's an idiot.
7. His communication is terrible. His pronunciation requires you to ask for repeats again and again because he doesn't know which syllable gets the stress.
8. His speech is loaded with trendy buzzwords; stories, refactor, technical debt. Nothing he says actually "means" anything.
9. He talks reverently about all the latest fads (test-driven development, pair programming, scrum) and clearly believes this marks him as a sophisticate.
10. When he checks his calendar you see that every day is loaded with meetings.
Edit: if you capitulate to the whiteboard BS you are given a problem that hasn't made sense in a quarter century. Linked lists, binary trees. We have container classes and methods now.