Complex sentence: Since then, most linguists (among them Louis Remacle), and gradually also Walloon politicians, regard Walloon as a regional language, the first in importance in Wallonia, and the only one to have originated from that part of Belgium.
Split into simpler sentences: Since then, most linguists (among them Louis Remacle), and gradually also Walloon politicians, regard Walloon as a regional language, the first in importance in Wallonia. It is the only one to have originated from that part of Belgium.