A how-to pdf of The Writer’s Studio Guide to Publishing in Literary Magazines and Entering Contests by Ayelet Tsabari. It includes,
Rejection with an open invitation: almost always follows a personal note and feedback. Nothing nicer than having the editor add: ―I would love to read more of your work!‖ It‘s
the best next thing to an acceptance letter. Do take them up on the offer and consider
them when sending out submissions.
Oh darn, got one of those and considered it polite rather than tier 4 up from form letter no.
[via the Literary Type]