Is there any protocols to identify what sort of document MS-408 is?

[Jorge_Stolfi]

Can we say that a low H0 is not itself evidence of low information content or of non-language? An encoding choice can easily depress symbol-level entropy while keeping the overall information rate of the message completely intact—effectively just redistributing how that entropy is packaged.

Correct, but not just h0.  One can manipulate h1, h2, etc as well.  

However, attempts to compute hk of a 100'000 character text for k greater than 3 or 4 will yield a meaningless number, because there will not be enough data to estimate the required probabilities.

And the entropy does not measure the rate of meaningful information.  It will count the bits of random nulls, spelling errors, and random spelling variations together with those from the meaningful message.

All the best, --stolfi