You can do what you like to some extent (depending on the location), there's no set etiquette for a church, certainly.
its becoming too much of a topic.
I agree, if people believe in respecting the fallen then they should do so, and they should do it in whatever way they prefer. If they would rather sit down in quiet contemplation, power to them. If they want to stand to attention, good for them.
If others want to just get on with other things, I support that too, as long as it's not disturbing the former groups.