1. A lot of people recycle the same image folder over and over again - if you spend enough time here, you will catch up on it quickly.
2. Certain minor percentile of posters use /bant/ specific extension to recognize each other with funky flag patterns.
3. If you think that you don't have a particular post writing style, you are probably too accustomed with it to notice it. Some people spend here way too much time and recognize these things.
BONUS upper level of autism spectrum:
4. Be knowledgable enough to recognize whenever somebody is posting from a phone image folder or regular PC.
Extra for guessing when they took a shit today, solely based on archived posts.