Why is it necessary to manually enter a message for Facebook in certain places?

In certain places within Buffer, including the Buffer browser extension and the Share Again feature, we will pre-fill the composer with the title and link. However, you might notice that we're not pulling in this information for Facebook accounts. Facebook rules stipulate that third party apps, such as Buffer, cannot auto-fill the text update for a post on behalf of users, which means users need to directly input what they'd like to share. We're sorry about this limitation. We're keeping a close eye on Facebook's guidelines to see if this changes in the future.