Putting a sign up is not a bad idea, but get the BC to do it so it is on BC Letterhead and carries more weight. Most door closers will have an adjuster somewhere, though.They have a mechanism at the top of the doors but I don’t think they have any settings so to speak. Also they’re button-press-and-lock only, no key lock or deadbolt, so they lend themselves to people pressing the button and letting it slam shut.
I’ll add it into an email about other issues I have about the place. Am tempted to put a sign up in the meantime requesting ‘nicely’ for people to be a bit more considerate