Is there a way to refer to a previous post I gave in a thread, in a new answer to that same thread?
Could posts in a thread, be numbered for instance?

Not directly, no. Years ago we counted posts (#1, #2, #3, etc) but that didn't work because if a post in the middle of the thread was subsequently deleted, all of the posts after that were renumbered.

You can link directly to a specific post by clicking the timestamp within it to go to its permalink.

OK got it. Thanks Dani. :)

The date-time stamp on a post gives you a hard link to it that can then be pasted into another post.

For example

I said that already :-P

I said that already :-P

I had my post composed and got distracted. You had replied by the time I clicked Submit.