Assuming your online identity is secure by obscurity is not a realistic option. If all it takes is a flashlight for everyone to become “vulnerable”, we need to just assume the light is always on. Someone handing out flashlights just highlights the bigger problem.

If this truly causes worry, adopt better opsec and create generative usernames for different sites. If not, assume anyone will easily be able to link your bowel issue subreddit comments to your LinkedIn profile.