[ars]

Perhaps I've misunderstood, but I think it's not the text that is unicode complete, it's the transliteration rules that are.

Unless you install special rules you won't be doing extra computation.

[pwdisswordfishq]

Not even any built-in transliteration rules, but the transliteration rules engine. One has to load a custom ruleset to exploit it – and I presume no sane implementation is going to accept rules from untrusted input.