I'd argue that "PC" has two meanings then. I'm going for "non-Mac PC", since that's what the title implies by separating Macs from the rest of PCs, and because I don't feel sensitive to exclude a huge set of possibilities.
It definitely has two meanings in the same way that "hacker" does and it is all contextual. If I hear hacker outside of this website I usually assume it is being used derogatorily.
In the "I'm a Mac, I'm a PC" context there is no confusion what PC means. In Hacker News context I can understand how the term PC might be ambiguous. I am really arguing that at this point though even hackers are calling Windows machines PC's. Although I have always wondered why everyone refers to them as PC's I have never found myself being confused when I hear it nor have I ever been misunderstood when using the term.
Exactly, that's why I assume everyone who is on Hacker News is aware of the Linux branch of operating systems, and at least isn't naive enough not to consider them in this kind of choice.
In the "I'm a Mac, I'm a PC" context there is no confusion what PC means. In Hacker News context I can understand how the term PC might be ambiguous. I am really arguing that at this point though even hackers are calling Windows machines PC's. Although I have always wondered why everyone refers to them as PC's I have never found myself being confused when I hear it nor have I ever been misunderstood when using the term.