Is there any way to add a note to the top of one's WL, like we can add a note to the top of our bookshelf?  For instance, "I will take ARC's, PM me to work it out" (I personally don't want ARC's, but that's just an example).  Or, "I'll take any version of a book, so if I've just got HC listed, but you have a PB, PM me the isbn and I'll add it".  Or, "For textbooks I cannot take alternate editions, so please don't offer.  Thank you". 

I don't mean to take the place of RC's, like, "only post to my WL if you're a non-smoking house".  I was just thinking of something that might help cut down on communication and time.

Not at the moment there isn't. Also when posting to FIFO you don't see the person's WL and I'm not sure how many people would think to look there.  I think TPTB assume you will add any version of a book to your WL that you are willing to get and won't add the ones you don't want. 

 Plus I can also see where people might abuse this and puts notes in there like "I will give 2 credits if you can post this or that book to me" or something like that.