I can understand the idea behind implementing this as a feature. It's similar to rating movies or books, it gives people a general impression if the content would be worth their while.
That said, just like movies and books, that system can definitely be abused, or not accurate to one's taste. (I've read highly rated books that I hated, watched low rated movies that I loved, etc.)
It can for sure be disheartening for the creator on the receiving end though. I would just do your best to ignore it, and just stick with your comic. If you want to try improving things when and where you can, go for it, but like others said, it's a free comic that you're sharing, you have no obligation to do anything for your audience. (Not to mention, those who typically rate one star are probably not your target audience anyway, so it's likely not worth your time bothering to please them.)