1. the one or ones being addressed
2. ONE sense 2a (which is “being one in particular”)
So, pro tip: in chat-like discussions with strangers such as hacker news, one should prefer saying “one” when using sense 2, even if it sounds a bit archaic (at least to me. Is it?)
Also, when reading a “you” that could be interpreted both ways, do not assume it is used in sense 1.
I do agree that it's surprising behaviour to regular users of PDF that it usually maintains a history of sorts. Apps should make this clearer.