Matzav.com is reporting on a p'sak (halachic decision) by R. Eliyashiv regarding making a mezuman by the seder. He says that normally three people who eat together are required to make a zimun. However, he says, there are two cases on the night of the seder when three people eating together do not make a zimun. I'm going to present the second one that Matzav.com reports first.
1. People who eat together on Pesach but are makpid (particular) not to eat food that is prepared by others on Pesach. Since they cannot share each other's food, they are not counted for a zimun.
OK, that sounds logical to me. They may be eating in the same location, but they're not really eating "together." The other case is as follows:
2. A group of people where some only eat hand matzah and some only eat machine matzah. "Even though this is only a chumra," reports Matzav and in reality, they *are* allowed to eat each other's matzah, they cannot join for a zimun.
The second ruling truly surprises me. Here you have people who, by choice, are not eating each other's food, and they are not able to join for a zimun.
How is this really any different than if my two friends and I go to a fast food place and they order a burger with tomatoes (I hate tomatoes!)? I, by choice, am not eating their food -- and perhaps they don't like my choice of food. Does that mean that we cannot join for a zimun?
(Please, no snark. Serious discussion only)