Actually that won't work. Submission doesn't have interaction_counts -- sources have a single interaction_count. The only place in the submission that stores this count is within the filename, so there isn't really anything to sort by except the filename.

What I already did there is a little hack to sort numerically instead of alphabetically.

It could work to refactor this and make it so each submission does indeed have a field like interaction_count that can be sorted by. Or we can keep it like it is.