request_uri() returns incorrect URI for some builds of IIS7

Some IIS7 builds without a MS hotfix set $_SERVER['REQUEST_URI'], but fail to include the query string. This WordPress forum post includes a simple workaround, but I don't think we want that as it would lead to incorrect results in situations where Apache rewrite rules add an internal query string to requested URIs that do not have one. That post is also several years old, so I don't know how many broken IIS7 builds are still in wide use.

Is this something we should worry about? Fix? Document?

Related: #1547294: Documentation for request_uri() incorrectly says that only Apache provides $_SERVER['REQUEST_URI']