Not really sure if you'd call this an error but it would be nice if it did cause an error ;)
If you are using an xml modification file and misspell a tag the manager won't complain.
I.E.
<file name="$sourcedir/ManagePermissions.php">
<operation>
<serach position="before"><![CDATA[
'profile_remote_avatar' => false,]]></search>
<add><![CDATA[,
'profile_ignore_board' => true,]]></add>
</operation>
</file>
Did not cause any time of error or warning during installation (it did during uninstall of course). In fact it said that ManagePermission was successful :)
I'm not sure how feasible it is to have it output an error but it should would be nice