you are way off the mark - this is what happens to spoilt votes, they are piled up, a time is set, an official states the reason for not counting the vote - the voting paper is held up, anyone present can agree or challenge the reason.
"anyone present" is generally a maximum of one person from each party, normally the most bored person who has already had their maximum possible caffeine intake and thinks a walk over to the odd corner where this is done might help them stay awake - often parties send nobody at all.
This is done several times, in several corners, but really, nobody cares what is written, or even sees. They just stand where they can see yes, the paper is spoilt, but not close enough to see how.
The only discussion is ever about "voter intention unclear" because sometimes a tick has narrowly missed a box, and it is actually fairly evident which box, for example, then people take it in turns to approach and look carefully and then say if they think the voter intention can be assumed or not.
I have stood by these and looked carefully at ballet papers, looking specifically for the ones that say "adult human female" or similar. There are some if you look, but mostly you have to position your self right at the barrier to see, and people generally don't and they don't even look in the general direction, a lot of the time.
Even me, trying to read the papers often can't. Some just have one word messages, like WANKERS or something written across them, and if it is large and clear it might be visible
so voting papers that are disqualified are disqualified in an open and transparent manner, but that means people check the procedure is open and transparent, not that they check the individual papers.
no one sees what is written on them beyond the counter who removes them and the official who holds them up, and they probably don't care.
So if you are going to write anything, mega large and short and maybe in a thick red pen, or something,- and more people will see it, but probably not politicians, and noone will really be counting or remembering