There appears to have been a change in behavior in Service Request Offering design using the “Read Only Text” field using URL's sometime around 2015.x. We have a number of offerings which link people to more information e.g. a KB article, an external website, terms and conditions etc. In 2015.2 the read only text (label) element will no longer accept any website hyperlink in the value field.
This was not an issue in the previous versions and is essential to many of our offerings.
In newer versions, the Value expression entry form appears to object to the quotation marks normally used in the HTML to create a URL link. Removing the quotation marks allows the URL to be saved, and the link then works properly in the offering field.