Unicode. This effectively precludes all the sign languages in the world from having their Wikipedia. As a consequence all the modern software will not be able to be used for text in SignWriting, the only script that makes it practical to write a sign language.
Michael Everson has produced a proposal for the inclusion of SignWriting in Unicode. Have a read and, you will learn the complexity that comes with a proposal for the inclusion of a script like SignWriting in Unicode.
You will also read that this project was financed by the Center For Sutton Movement Writing.. that is to say by Valerie Sutton herself. If any of the chapters are looking for deserving projects they can fund this is one. This will benefit all the sign languages in the world. The list in the PDF of sign languages that are already written in SignWriting is impressively long.