It's really your call here whether you wish to make it private or public, as you mentioned that you're not uploading any videos yet, it's fine to keep it private or you can even keep it public as it might draw some attention towards you of those channels on which you're commenting videos, there might be chances that they might notice you and even subscribe you and in future, If you ever wish to upload video it might be easy for you to find your target audience here but I'd not recommend you to keep your subscribers count private once you start uploading as most of time, general audience believe If you can't be open to them and share your subscriber counts, it might create some sort of distrust or trust issues and some might even believe that If you're hiding your subscribers count there might be something wrong. Again, it's all that people might think, despite everything, I have had seen people hiding their subscribers count until they've reached some specific subscribers milestone, so in end, it will be your call. If you ask, we would suggest keeping it public as there's nothing wrong in hiding your subscribers' count (when you start uploading) or being ashamed of having fewer subscribers, it's all about starting and everyone starts at lower numbers.