If philosophy admits the existence of entities that cannot be sensed (which, granted, many philosophers have done), it is opened to all sorts of metaphysical horseshit.
This is imprecise. You have some evidence of some HN-posting entity, because you see a post on HN. That's not the same as theorizing the existence of other, unseen, entities that could potentially post on HN but never will.
Perhaps you meant rather that you've given me a free pass on the Turing Test, or the equivalent for "dogs on the internet". Thanks, I guess, but I don't see what problems that solves, and anyway it's still about the nature of a sensed entity rather than the existence of an unsensed one.