Well, I watch Youtube all the time and I got the idea that I seem to have seen some messages there. I'm not sure if Youtube can be used as a messenger, but if it is possible please tell me.

I don't know such a function either, but I googled it and it seems there is something similar. Anyway, I found an article with instructions on how to contact someone on youtube. Look, everything is written there step by step, so I think that you will find something useful for you. But I probably agree with the previous comment that Youtube isn't the most convenient platform for communication.