A mark could just be an offset inside the Text buffer instead of a direct pointer. Yes, dereferencing a mark would be slower, but do you really think that matters? I mean even if you did that 1M times/sec there wouldn't be a noticeable difference to the user.

On the other hand, look at array.c. Or buffer.c. Or map.c. Or all the manual linked list management stuff. Or all the other logic that would be so much simpler with a more functional language. I mean, sure - there's an unique feeling to being so close to the metal, and that's fine, but if you want to build something new reinventing the wheel for the millionth time is a waste of time.

edit: there are compiled higher-level languages too (i.e. Haskell). If you want minimal dependencies, it doesn't really matter how the binary got built.