@Senya_loves_choco Ahhh, is that so? Well, I have never encountered something like that since I'm still quite new to Wattpad. Maybe it's just a comment you don't remember and just suddenly, pops out of no where. Or maybe it's just a glitch that I think you should not worry too much about.
But considering the possibility of someone hacking your account, I suggest you backup your books so that you'll not lose them in case your account really gets hacked.
Another possibility is that your account is connected to another device, which is used by a relative or friend of yours, that has wattpad and reads there as well. They may not know that they're using your account and have commented by using it.
If none of these are applicable then all I can do is pray that you'll find a resolve on this problem. I really hope that wattpad wouldn't give you anymore problems so that you focus on your daily life and writing chapters for us, your faithful and loyal readers.