While leetspeak once allowed hackers to trade secrets on bulletin board systems, that model of simple letter replacement and misspelling is not a match for modern web bots. Spellfucker borrows from visually similar Unicode characters (much like Mimic does in code), as well as swapping entire syllables with phonetic similarities – better suited to fool automated filters that might trigger human content checkers on FB and Instagram. However, as pointed out on Hacker News, not all generated text from it passes the search engine test (passing Lionel Richie lyrics through DuckDuckGo).
Apart from the AI-hostility, an obfuscating language slows down the reader and forces them to consider each word individually. If this is not your aesthetic goal, there’s also the bbboing obfuscator, which offers its own weirding of language, using strictly letter scrambling. Its creator insists that, “rscheearch at Cmabrigde Uinervtisy" says the order of letters don’t impact reading understanding significantly, and such words can be read “wtoiuht perblom.”
If neither of these tools is quite your style, there is also Text Obfuscator, which has “levels” of obfuscation. While the lower levels are stripped-down versions of Zalgo text, the “leet” setting gives just barely shy of completely unreadable ®£5|_||†$.