(I also suspect that some spammers may read this thread to get ideas as to how to make posts with a sufficiently large character count without having to write something coherent.
If spammers are doing this, I'm not quite sure what their goal is: if a manager is simply checking post quality by using the metric of raw character count, then it doesn't seem like a situation where you need to exercise this much discretion. You could probably get away with much more.
Here is my makeshift spoiler, using the [abbr] tag:
█████Hopefully you appreciate this as a useful alternative. You just need the inner character, but it behaves functionally identically to [spoiler]