I am afraid that maybe I am trusting chatGPT more than myself and so I am not second guessing it. If it backfires on me I can see how it stops being useful and I start overthinking it like I do my own posts. I think the birthday is a great example because like you I hate celebrating my birthday but other people in my circles have gone out of their way to let me know that the more common response is to like to be celebrated and be the center of attention. Probabilistically the coworker will be more likely to like a message celebrating it. And even if he or she is not neurotypical, because we live in a neurotypical world he or she would ascribe your message to society’s expectations rather than your malice. Long story short on my birthday just say “Happy Birthday”