diff --git a/src/applications/diffusion/editor/DiffusionURIEditor.php b/src/applications/diffusion/editor/DiffusionURIEditor.php
--- a/src/applications/diffusion/editor/DiffusionURIEditor.php
+++ b/src/applications/diffusion/editor/DiffusionURIEditor.php
@@ -347,11 +347,11 @@
                 continue;
               }
 
-              $io_type = $uri->getIoType();
+              $io_type = $uri->getEffectiveIOType();
 
               if ($io_type == PhabricatorRepositoryURI::IO_READWRITE) {
                 if ($no_readwrite) {
-                  $readwite_conflict = $uri;
+                  $readwrite_conflict = $uri;
                   break;
                 }
               }
diff --git a/src/docs/user/userguide/diffusion_uris.diviner b/src/docs/user/userguide/diffusion_uris.diviner
--- a/src/docs/user/userguide/diffusion_uris.diviner
+++ b/src/docs/user/userguide/diffusion_uris.diviner
@@ -239,6 +239,11 @@
 authorities: the observed remote copy and the hosted local copy. Take the
 other URI out of //Read/Write// mode first.
 
+WARNING: If you observe a remote repository, the entire state of the working
+copy that Phabricator maintains will be deleted and replaced with the state of
+the remote. If some changes are present only in Phabricator's working copy,
+they will be unrecoverably destroyed.
+
 **Mirror**: Phabricator will push any changes made to this repository to the
 remote URI, keeping a read-only mirror hosted at that URI up to date.
 
@@ -251,6 +256,11 @@
 hosted by Phabricator by adding that other repository's URI, although this is
 silly and probably very rarely of any use.
 
+WARNING: If you mirror to a remote repository, the entire state of that remote
+will be replaced with the state of the working copy Phabricator maintains. If
+some changes are present only in the remote, they will be unrecoverably
+destroyed.
+
 **None**: Phabricator will not fetch changes from or push changes to this URI.
 For builtin URIs, it will not let users fetch changes from or push changes to
 this URI.