At Manifest 1.0, several people threatened to not attend if Richard Hanania was allowed to attend and/or speak. Manifold ended up prohibiting him from being a speaker, but allowing him to attend.
(Further background and discussion here, here, here, and here.)
"Due to threats" refers to Manifold making the decision not out of their own personal preferences, but because attendees threatened to not come or to do something else that Manifold finds detrimental. This includes justifications along the lines of "more people dislike X than like X, so it's utility-maximizing to ban them". It also includes situations where the threats were implied, such as lots of people aggressively telling Manifold how uncomfortable they would be if X were to attend, without explicitly threatening any action.
If Manifold doesn't make their decision process public, I'll take my best guess. I won't bet.
Related questions
seems quite possible that someone, in one message, would both bring to our attention something that we weren't previously aware of that causes us to no longer want someone to attend and/or to give them a free ticket, and in the same message tell us that they would pull out of attending if we didn't drop the other speaker.
compare:
we invite alice and bob to speak; bob says "alice did X thing, if you don't bar alice from attending then i'll drop out of the event;" we think that X is obviously beyond the pale (e.g. alice committed homicide or assault or something); we uninvite alice because her behavior was beyond the pale.
we invite alice and bob to speak; bob says "alice did Y thing, if you don't bar alice from attending then i'll drop out of the event;" we think that Y is not beyond the pale (e.g. alice made the case that electrons don't have qualia or something); we uninvite alice because we don't want bob to pull out.
in this case, i think (1) should not make this market resolve YES, but (2) should. and i think (1) is vastly more likely to happen than (2); i think we're pretty unwilling to bend under pressure per se, but much more willing to change our minds based on changing evidence.