Moving this to off topic. ULX has no 'queue' chat ability.
It does have a anti-spam chat ability, but that would actually prevent the chat from appearing at all. By default, it's set to 1.5 seconds.
If someone says something in less than 1.5 seconds before the last time they typed something, it wouldn't show up.
The description you give is indicative of lag due to, as the previous post states, network lag / high pings, or additionally, lua chat hook performance due to slow server processing.
Both would also appear in other delayed reactions to (such as time it takes to spawn props).