The construction “Hearing a cat crying at this hour is downright scary” is grammatically and semantically perfect. I don’t see any awkwardness in it. You just happened to have tweeted a sentence with the gerund phrase “hearing a cat crying at this hour” as subject, and with the progressive verb form “crying” embedded in it—a sentence that sounds perfectly natural despite your misgivings about it. If you change that sentence to “Hearing a cat cry at this hour is downright scary,” you’d be saying something else—that the cat cried only briefly and definitely not in a sustained wail, which is a sense different from the continuous crying evoked by the progressive form of the verb in your original sentence. Then, if you change your original sentence to “To hear a cat crying at this hour is downright scary,” you would no longer be saying that you were hearing the continuous crying of a cat at that particular hour; instead, because you are now using the infinitive phrase “to hear a cat crying at this hour,” you would be referring to a hypothetical scenario in your mind—the thought of being downright scared to hear a cat crying at that particular hour.
These are the semantic differences we’ll normally encounter when we play around with infinitives and gerunds alternatively to express the same idea. Sometimes, depending on the operative verb we use, the infinitive version and the gerund version will mean practically the same; sometimes, only one of the versions will mean what we want to say. (
“Is there bias against infinitives?”) Making the right choice primarily depends on our mastery of the semantic differences between infinitive expressions and gerund expressions of the same basic idea. At times, though, those differences would be almost imperceptible, and it is then that we need to play it by ear. This because although bound by specific grammar and usage rules, writing or speaking in English—as in every other language—is an art form that gives lots of latitude for individual style and self-expression, and one that can yield a thousand and one shades of meaning for the same basic idea.
