I am not telling anyone what to do. I am giving information. This is because I have seen how posters are treated on other threads giving this information, and it isn't very nice!
Do what ever you want, but here is some information about spoilt ballot papers.
If you write on your paper, whatever message, it will NOT BE READ. Except maybe by the counter that puts it into the spoilt ballot paper list. But only if they have time to read it, mostly not.
It will be held up and agreed to be spoilt, in front of a committee open to all parties. but they won't read it, and the person holding it up won't read it. No one has time. Many papers are spoilt. Everyone is tired and busy. No one will be standing close enough to read the words.
There is a lot of talk about spoilt ballot papers being scrutinised by candidates, and this is how to get a message across to them.
NOT TRUE
Ballot papers are not scrutinised if they have been written across.
I have a list of circumstances when I might ask to inspect a paper closely, and papers written on don't come into it. I would not waste my time or anyone else's time on a paper that is clearly deliberately spoilt, because the business of the night is count votes, and there are literally tens of thousands to count, and that is clearly not one of them
The ones that are scrutinised are the ones that MIGHT have a valid vote on them.
So if you want to put a message on your paper to be scrutinised, then it must have something on it that might be counted as a valid vote. That way, people in the confirmation committee will be looking closely at your paper, and only then will they see the message.
A paper that is signed is invalid if the signature can be read.
If you want to spoil your paper then you need to make it worthy of discussion, about whether it has a vote on it or not.
So I suggest a CLEAR vote, for whichever party you dislike least. And your written comment that you want to be read. And a scrawled signature, which is not your name, and not legible.
This, I think, might get your comments read by agents of different parties - because they will be discussing whether this is a valid paper or not, and does that vote count, and is that signature legible. Your vote might or might not be counted in the end, probably not, but possibly, so don't do this if you definitely don't want to be counted.
Of course, the message might still not be mentioned to the candidate, or to anyone else at all, but this is the only way I can think of to get comments on a spoilt ballot paper read, because otherwise it doesn't happen, it is just a count for the spoilt paper party, and no one knows or cares why.