I've come across a few questions on Programmers that got migrated from SO, closed as "not-constructive", and then locked by the Community user.
I'm assuming the lock is to prevent the question from getting kicked back to SO as a "rejected migration", however it also prevents the questions from ever getting edited and reopened. It also prevents comments to explain the closure to the OP, or to help them improve the question, or asking for any kind of clarification.
Recent examples I've come across: here and here
Can you make the Community user stop locking migrated questions that get closed?
(I think this only happens with some close reasons, as I noticed closed-as-duplicates do not get locked)