The error reporting from failed writes for the pos files that updateSearchIndex uses and checks could use better error messages to make fixes for problems more discoverable for naive users. Perhaps instead of just "Couldn't write to the searchUpdate.XXX.pos!" the message could read "Please specify -s FILE to give a a writable location for the position file".
Alternatively, if the file isn't writable, the lock time could be set to infinite, a message printed saying what was going to happen, and, after confirmation, the script would continue.
From the support desk:
When I run maintenance/updateSearchIndex.php I get the error
--- Unlocking -- Done *** Couldn't write to the searchUpdate.MyWiki.pos!
Does the maintenance directory needs some write rights?