Everything written in those three sentences you've highlighted from the article is correct. You may not like how they've chosen their three sentences, but these

Everything written in those three sentences you've highlighted from the article is correct. You may not like how they've chosen their three sentences, but these three sentences contain no lies. Every negative number has 1 as it's first bit, every positive number (including 0) has 0 as its first bit. Therefore first bit encodes sign. The other 15 bits encode value. They may not use the normal binary encoding for negative integers as you'd expect from how we encode unsigned integers, but you cannot explain every detail every time.