Okay, thanks for responding! Its pretty tempting to remove trails from OSM to change others behavior, but that's counter to OSM core tenets, the idea is to accurately represent everything how things exist. OSM data is not only used by the MTB community.

I restored the path, changed it to informal type, and applied the tag "bicycle=no", feel free to add any other tags or restrict the access farther by adding things like "access=no". This should make it clear in other apps like AllTrails that access is not allowed.

You might have already, but the best way to close a trail for good, is physical barriers and good signage on the ground. Once the trail is truly gone and, then it should be removed. 