[marktwain]

There is no such thing as shared hallucinations.

There is such a thing a shared false memories.

I recall, but do not have a source, that such a thing has repeatedly been demonstrated.

There is an event. Someone claims something happened, which did not, in fact happen, and the "false memory" spreads by word of mouth.

Soon, a significant number of people remember the claim as reality.

Even the orignator of the false memory may have mis-interpreted what happened.

[reasonisfaith]

“There is such a thing a shared false memories.”

Not on the scale we’re dealing with. You can forget that argument.