As bad as legalism is - the adding of extra-biblical rules to either define sin and righteousness or to add requirements to salvation - the extra emphasis placed on outward appearances as part of that legalism is much worse. A church can teach no drinking, no smoking, no dancing or no going to movies in its legalism and produce some self-righteous people, but when it teaches to refrain from making any outward appearances that reflect any of these things in the way we live, dress or move to a new apartment, it can create some pretty hard core Pharisees with very toxic doctrine.
I've had the misfortune of attending several churches where a heavy emphasis was placed not only on do/don't rules, but on outward appearance. Or maybe it was fortunate in a way because now I know how to notice those things and avoid them, and tell others.
One of the verses often twisted out of its true meaning is 1 Thessalonians 5:22, "Abstain from all appearance of evil." KJV I'll give an example of how this is used with relation to drinking, smoking and moving to a new apartment. Back in the day before either self-storage or cardboard recycling became popular, when people had to move the best source of cardboard boxes to pack one's belongings was the grocery store. So, we'd go to the store and ask for boxes, and the stores were more than willing to give the boxes away because that relieved them of breaking all the boxes down and placing them in the garbage dumpsters. Many of the boxes were empty cases that originally contained alcohol and cigarettes. So when you moved, those boxes were visible to those who helped you move or to bystanders in your new and old neighborhoods. By using a Marlboro or Budweiser box to move, the outward appearance driven legalists would claim that you were giving an "appearance" of evil, even though anybody with half a brain could deduce that you were merely using discarded cardboard boxes to move. It simply didn't matter. This placed a heavy burden on anybody when moving, because they had to take extra care to pick and choose wisely which boxes to use.
Another personal example is in driving expensive cars as giving an appearance of evil of spending lots of money on vanity and ego when you could drive a modest car and give the rest of the money to print gospel tracts or similar spiritual things. My brother has spent his entire career in the auto service/repair field. The shops have great policies for family members of employees, namely that repairs are performed "at cost." Our m.o. was to have me swap cars with him in the evening, and he would drive my car to work the next day, have it fixed, and swap back that evening. Well, one time my brother got a great deal on a used BMW 5-series car, and I needed a repair that could only be performed over the weekend. So we swapped cars...and it dawned on me that I had to drive to church on Sunday! In a BMW! The Pharisees would certainly notice my display of vanity (it would be assumed until proven otherwise that I was acting quite worldly), and I was trying to figure out how to park several blocks away without anybody noticing, etc.
Every area of life imaginable was subject to the outward appearance nazis, and they certainly made their fair share of comments about anything you could imagine. They also made their fair share of judgments about people in their hearts without ever saying anything, thus condemning others without anybody (except God, hahaha) knowing about it. I should know, I was taught to be such a person, and it wasn't until later that God was merciful in showing me the tyranny of this way of thinking and living. Your rich uncle buys you a pair of designer sunglasses (costing nothing to you)? Tough, you're putting worldliness on display. Being thankful to God and your rich uncle for providing a helpful item at no cost, is, well frowned upon becuase of the outward appearance.
People subject to this type of legalism can be spiritually crippled for a long time, even eternally. We shoud instead learn from Jesus when he says, "Do not judge according to appearance, but judge with righteous judgment.” John 7:24.