I think itch.io seriously lacks good visibility balancing. Not sure what they're doing under the hood but the submission page seems entirely random.
Ludum Dare has a filter selection, the default of which bubbles up games that have a high rating ratio. That is to say developers that rate more of other people's games gain more visibility: (ratings given / rating recieved). On the whole it works pretty well for maximising vote distribution relative to participation, and minimised the reliance on devs spamming for attention - though this still happens to some degree.
I would be keen to raise awareness of this to the GMTK team and see if they can action any structural changes for the next jam.
==Edit=================
Just noticed itch.io does have a submission filter, but it IS random by default and there's no natural balancing. Also I expect most people use the default filter. It make sense for itch.io core game library, but not during a voting period for a jam in my eyes. Thoughts?
Current filter options:
* Popular
* Random (default)
* Least rating
* Most ratings
* Submission order
* Most recently submitted