I'm creating a record via a M/R script and on that record, I have a User Event script with an afterSubmit entry point. Will this User Event script get triggered when the M/R script creates the record?

yes

Thanks for confirming!

easiest question I've ever seen here 😂

we all deserve a softball every once in a while 😂

FYI the User Event deployment can have a Context Filtering, where a Map/Reduce context could have been included or excluded. If the Context Filtering is blank (the default), then the UE script does run on Map/Reduce

But there is no way to tell which script triggered the UE right?

I am not aware of any method to know which script that triggered except to set a field from M/R script. You can remove the value in U/E script after analyzing it to make sure it's not stored. Very hacky, but the only method I can think of.

Thanks for the thoughts Marvin!

Some throw an error and examine the stack, that’s a trick that’s used