On: Charset="WTF-8"

[KPGv2]

I could answer your question better if I knew why you need to detect Zalgo-isms.

[account42 → KPGv2]

Because they are an attack vector. They can be used to hide important information as they overflow bounds (can be solved with clipping but then you need to do that everywhere it matters) and have the ability to slow text renderers to a crawl.