Just to add onto this good answer, you are really only expected to tip for sit-down restaurants with service and bars.
For takeout, cafes, fast food, etc., you don't need to tip. A lot of places these have payment machines that just ask if you want to tip by default. You can safely hit "No tip" on these if you don't want to.
Ostensibly it's just to replace the tip jar for those who don't use cash, but the prompt appearing every time you pay by card has convinced a lot of people that tipping is what you're supposed to do in those situations, when in reality you have no obligation to.
One of the admin accounts appears to have been compromised. The owner/other admins appear to be aware now because that account had its admin access revoked and offending posts are being removed.
Definitely opens up a big question about the security of Lemmy instances that I am sure will be discussed over the next few days.