I have a couple books that have someone's initials printed in marker near the top of the book (in small lettering).  The books are in otherwise good PBS condition.  Is this ok?  I checked the help docs but couldn't find anything about writing on the cover, just the pages.

TIA!

there is no rule that i have seen.  i have my name stamped in most of my books so if that were a condition, i would have to take down alot of my books (not all on my bookshelf were my personal books but some were)

Small amount of writing is allowed on inside cover, so I think it would still be postable on PBS with small amount of writing on cover as well.  Help section specifically vetoes writing on the "text pages" which is not the cover.

From help pages: BookCrossing books may have stickers or stamps or markings on the outside or inside covers or page edges of the book; this is OKAY. 

Since BookCrossing books can have "markings on the outside cover" I believe all books can.

So, I think your book is postable.

Here is the link to the conditions guidelines pages I used for reference.  http://www.paperbackswap.com/help/search.php?terms=writing+in+book  then click on Book Condition Guidelines

Thanks - I may test it with a small amount of nail polish remover to see if it will come off.  If not, so be it.  More opinions welcome!