User blog comment:Kirkburn/Technical Update: September 21, 2015/@comment-5226524-20150922144113/@comment-126761-20150922144655

Some communities previously used a hacky method to add a guidelines link to the right rail chat module - but that no longer works. Since adding a guidelines link is a pretty simple desire, we added this new message to make it possible. If you don't make use of the message (which is perfectly fine!), nothing will change.