My Dad did ballot counting and if you put a Tick or some other clear mark then generally your vote is counted as a vote; the candidates get to decide which potentially spoiled ballots to accept (I believe that all candidates have a veto on accepting each ballot) and mostly any clear intention of a vote is counted. Whereas of course "you are all cunts" is clearly not a vote... (not very nice though).

However I too would like an official "none of the above" option that was actually counted. Maybe it would encourage other people to stand?