I have had my top-spec, fully loaded 2018 MBP for a few months now and recently noticed an increasing incidence of repeat keystrokes, mostly from n, m, o and space-bar. Diddling with the Preferences settings for key-repeat accomplishes nothing. From the moment this machine was unpacked, it's had a keyboard cover on it, so debris ingress into the keyboard assembly should be minimal. From this and the many reports of keyboard issues after just a few days of use, I'm thinking it indicates a contact-material issue rather than a debris issue. If so, debris would worsen the problem but even cleanroom usage would not prevent it. (And no, I'm not an accomplished keyboard engineer, but apparently whoever cooked up this butterfly design isn't either.)
I'll register a complaint with AppleCare but can't afford to be without my machine for an extended amount of time. I can mostly live with this issue if it doesn't get worse. But it's not what I want from a nearly $4k machine.
I think the key here is that, it isn't stuck debris which causes this issue of double/missed keys but there is some fundamental flaw on how the product registers a key stroke. If it was merely dust, Apple would never have to replace keyboards and would just blast compressed air until it resolved itself.
There are other keyboards which had the same problem and they don't use butterfly keys (e.g. Keyboard chatter on the Aero 15X).