So if Miranda doesn't usually tweet about the history of Mexico, he can pick other texts (written by him or others) which would sound more plausible as something he might normally tweet.
Having said that, the middle dot is not as unobtrusive as I would like, so perhaps it's better to rethink that part of the system, using some of the other suggestions in this thread.
you could imagine a system which uses entirely normal and habitual tweets, but encodes information in choices of synonyms used in the text, or whether or not punctuation was used in certain places, or the timing of the tweet's publication. lower bitrates, but plausibly deniable as to the message's existence.
The classic steganography methods you're describing may appear less obvious (for lack of a better term), but they're also easier to break once the pattern is discovered.
Then what you're writing will be functionally indistinguishable from random.
hmm ... but maybe too random, humans are bad at being truly random - the entropy in your period usage will be too high ... perhaps xor the RSA output with a OTP of something 'random' you scribbled yourself on a page ;-)
... seemingly random bits, xored with anything not directly related to the bits in question produces seemingly random bits... There are other ways of transforming a sequence of bits to look less uniform, though.