Can there be a signature (not the author) on the dedication page?  It is not actually in the text pages.  Would this be an unpostable book?

This pertains to writing in a book.  

"-- no highlighting, underlining or writing on text pages (exception for Textbooks/Workbooks and travel guidebooks)"

So Lisa, it appears writing on pages that are NOT text pages is ok for swapping here. 

Thank you.

Over the years I've received and sent out many such books.  If you couldn't post books with a message from Mom or Uncle Fred saying they hope you enjoy this gift book, then the number of books exchanged here would drastically drop.

Unless someone has Requestor Conditions that ask for no writing at all, a signature on the flyleaf is okay.

The help doc titled "Book Condition Criteria for 'Swappability' at PaperBackSwap" has this to say:

No writing or highlighting or underlining on text pages

• a signature or note or written price on the flyleaf or inside front or back cover is OKAY
• a bookstore stamp or bookplate with previous owner's name in the front of the book is OKAY
• an author's signature on the title page is OKAY
• writing or highlighting or underlining on the text pages is NOT OKAY

This is followed by rules for specific exceptions for textbooks, travel book and cookbooks, with the proviso that the sender gets written permission from the requestor before mailing.

The Swappability page does not specifically mention it,  But, as I mentioned it was not on the text pages, so I just wanted to be totally sure before I posted it.  I personally would not have a problem with it, but I didn't know how others would react.