Spoilt votes are counted and feature in turnout %. So not quite the same as not turning up
Eh, yeah it is, because they also count those that don't turn up. 
You don't have a very sophisticated understanding of democracy and protest, do you
Well maybe not but I have a much better understanding than any one writing shite on their ballot paper and thinking it is either looked at by someone in power, or anyone who actually gives a shit. It's not.
It's counted. Like those who don't vote. Some council worker on a low wage will read them, lucky them. And then that's it. End of. They are counted like the folk who don't vote.
Anyone thinking it makes one iota of difference is fooling themselves. The only thing that matters is who you vote for. Unless you count the local council junior having to read through them trying hard not to get fed up of the large amount of cocks drawn on them.