Critique and Advice; the treadmill of adventuring.

I write a pretty serious tone adventure, but I balance it out with a cute art style and occasional comic relief. Don't be afraid to make jokes or take joke suggestions, but use your best judgement to determine whether or not it would be appropriate. Maybe the previous scene was really emotionally draining, so a joke or two would help lighten the mood. It probably wouldn't be appropriate in the middle of that scene, though.

But, in my experience, seriousness is not much of a determining factor for readership. If you have a small number of people suggesting on your story, chances are your readers are just having a hard time coming up with suggestions, which is a different animal altogether. The key to avoiding that is to have something interesting happen every update - if nothing has changed, or there is nothing to respond to, you probably won't get new suggestions.

In the end, I think the biggest thing you can do for yourself is just have confidence in yourself and your writing ability. The best way to improve is to practice, and I'd say just being aware of your shortcomings paves the way for improvement. Just keep trucking, and the rest will follow.