Never spell a word the same way twice?

A long time ago I was reading about Renaissance-era ciphers and I remembered this quote:

David Kahn, author of The Codebreakers, quotes Giovanni Battista Porta who published, in 1563, a famous cryptographic book, De Furtivis Literarum Notis:

"He urged the use of synonyms in plaintexts, noting that 'It will also make for difficulty in the interpretation if we avoid the repetition of the same word.' Like the Argentis, he suggested deliberate misspellings of plaintext words: 'For it is better for a scribe to be thought ignorant than to pay the penalty for the detection of plans,' he wrote."

This idea of deliberately misspelling words is intriguing to me. I'm wondering, is this a technique that could potentially be effective against modern mass-surveillance systems?

For example, in an NSA-style mass-surveillance system that flags certain designated keywords, could deliberate misspelling of words (in an email or SMS, for example) potentially be used to avoid detection?

the bobm is hdiden isnide teh parlaimnet biuldnig

The idea is that it would work sort of like a CAPTCHA, making the message obfuscated for computers but still human readable. Is this realistic?