[rayiner]

Relaxation of rules makes language less precise, and when phrases that mean different things come to mean the same thing, then expressing distinctions requires more words and clumsier constructions.

Also, take your example: "Language is comprised of rules that change over time." The correct alternative is shorter and simpler: "Language comprises rules that change over time." Most people don't even know that there are two perfectly good verbs "to compose" and "to comprise" that let you avoid the "is ... of" construction. If people see the clumsier construction in "good writing" they will never know that there is something better.

[atburrow]

Isn't your "Language comprises rules that change over time." statement invalid as well? The word comprises should be used when there exists a definite set of items.

For example: "That house comprises 4 rooms" versus "That house comprises at least 4 rooms". The second statement should be "That house is composed of at least 4 rooms" because the room count is not an exact quantity.

[rayiner]

I think you're right. In my head I was equating "language" with "grammar" and I think it's fair to say that you can specify grammar with a definite set of rules. But at least human language has more than that.