Well... Yes, voters are biased. It's nearly impossible for them
not to be. Bias is naturally wired into the human brain: We're more trusting of familiar things and we tend to stray away from unfamiliar things. If we enjoy a game, we're more likely to enjoy any content surrounding it. If we dislike a person, we're more likely to avoid any content they produce. We're hardwired to make comparisons, whether it be comparing a new TASer to an experienced TASer, an old run to a new run, games to other games, runs to other runs, et cetera. There's always a "best" and "worst" choice, and it's different from person to person, and unless the choice is something like "chocolate ice cream" or "nails being slowly driven into your flesh", people are going to be slightly biased towards one choice over the other based on what they like and dislike. It's not something we can avoid in the slightest unless all of humankind were turned completely emotionless and apathetic, having the exact same reaction to literally everything in the world.
We can compare this new run from TASeditor to other runs that he's done and it makes sense, which makes us happy as human beings. We've seen TASeditor make good and optimized runs before, so we're immediately biased into thinking that every run he makes is going to be good and optimized. We haven't seen a previous Jigwally run, so the only way we can make a comparison is to compare it to other first-time TASers submitting their first runs. For the most part,
first runs are highly suboptimal (and painful to watch in retrospect) and most of them aren't accepted, so our immediate bias to any first run is that it's going to be unoptimized.
Even if we get past being biased towards or against certain people, there are still a lot more bias obstacles to overcome. Honestly, the system works well because multiple people communicating means that everyone can keep everyone else's biases in check, and the ultimate decision relies on the judge who makes a decision that isn't just their thoughts, but everyone's thoughts.