ambiguity about informal postdoc offer
I replied,&quot;Thanks for the update! I could start at the beginning of xxx.&quot;

You're almost certainly okay. You haven't gotten the actual official offer, and though you've shown clear interest you haven't accepted anything. Of course, the PI involved could be disappointed, and if they're a jerk they could even retaliate by speaking badly about you. Unfortunately, though, just about anyone can choose to be a jerk whenever they want and it doesn't necessarily have to be a consequence of something you've actually done wrong.

I have since clarified to the PI during a call that I was considering other options and he did not seem too bothered

Now you are definitely okay. Some people would suggest this level of honesty is somehow not strategic; personally I think in most cases it's better to be clear. People who are hiring for a position should always assume the people they recruit are pursuing other offers, just as people applying for one should always assume there are other candidates.