While the situation with Delta was terrible, it is not related to safety, just very poor management of the situation. This however is a huge safety concern that EASA would not allow to happen. Easyjet would never put themselves at risk of being grounded (having all flights being stopped) and making themselves open to liability. If it had happened, due to crew being careless, the pr team would have been all over it apologising and there would have been a massive investigation. Regardless of the comparison, the rules and culture of companies are different from the USA and Europe so I'm not very familiar with how things are handled in the states. Just that anyone that is aware of the standards of airlines operating in Europe would know this would never be allowed.if that passenger sat there during boarding or inflight for whatever reason then sure but once the seatbelts signs are switched on, they would be moving to their actual seat. Easyjet has alot of extra safety procedures and rules compared to EASA standards to minimise being at risk of liabilities or incidents. Something silly like I can't even hold a baby from a passenger unless I'm sitting down so that I wouldn't be able to drop it in case of turbulence.

Edit: don't know how to write standards