If you think "m00n" vs. "moon" or "The" vs. "the" matters, you're not paying attention. A memorizable, but randomly composed string of words all in lower-case ASCII is significantly stronger than anything "complex" (for you, hardly for the cracker--common substitutions are basically worthless: they provide no entropy) you can concoct and remember.
Again, you're not looking at the entropy.
Anything you can generate without much more unpredictability from a plain English sentence is not a significantly better passphrase than a plain English sentence. Better? Yes. And I credited you for that.
I chose the passphrase "The Brown cow jumps over the m00n!" as an example not "The brown cow jumps over the moon." which is a significantly worse passphrase, especially considering every word is available in a dictionary.
The OP had trouble memorizing more than 16 characters for a passphrase so I suggested something easier yet still solid yet you seemed to think I suggested just a plain english sentence of words.