If I post a book directly to someone's wish list would they know that the book was posted directly to them  by me or will they think it came in FIFO.  Also the other way around if someone posts a book directly to my wish list, will I know if it came directly posted by them or through FIFO. In other words is there something that lets you know it was not through FIFO.

No, there is no obvious way for someone to tell if a wishlist book was granted through FIFO or by being directly posted to their wishlist by a fellow PBS'er.   PBS doesn't send a message or indicate this in any way.

However, if a member is, for example, 20th in the wishlist line for a book, and then it is granted to them - well, that's a pretty good clue that you didn't get it through FIFO.   Then once you have accepted the wishlist book, all you have to do is click on the PM button to find out who the generous member was that posted it to your wishlist.

If you're going to post a WL book to someone  - you know who you're posting to so you could PM them before you do it to let them know you're the nice person.

As Lynne said if you're down the line for a WL book and suddenly you're getting it unless a whole lots of people turned it down, someone was very nice to you...say tank ya very much!

I wouldn't do this without contacting someone first.  Many people are constantly short on credits.  So if you bump them quite a bit ahead on line by posting a book directly to them: they may have to turn down another book where they were at the top or scramble to find a credit.  I know a lot of members watch which books they are nearing the top for and plan their credit accordingly.  Just a thought.

ETA: If you got an offer for a WL book that you were several spots down for: it could have still come from FIFO.  I've posted WL books and had them go through several people before being accepted by someone.  So you could be 10th in line when a book is posted and it'll come to you between inactive accounts, RCS and people deciding they don't want the book.