Last modified: 2014-02-08 01:41:21 UTC
Search for "." yields "An error has occurred while searching: The search backend returned an error: Empty search" and for ".." it is "An error has occurred while searching: There was a problem during the HTTP request: 404 Not found". This is different from the usual page missing results.
Confirmed for lsearchd/MWSearch, not a problem with Elasticsearch/CirrusSearch. Marking as cirrus-fixed.
This problem does not exist in CirrusSearch. As we're in the process of migrating from Lucene to CirrusSearch, I'm marking this as RESOLVED WONTFIX.