We encoutered a situation where hbck was run by an under-privileged user that was unable to write/modify/merge regions due to hdfs perms. Unfortunately, this user was alerted of this after several minutes of read-only operations. hbck should fail early by having a write perm check and providing actionable advice to the hbase admin.
Maybe something like: "Current user yy does not have write perms to <hbase home>. Please run hbck as hdfs user xxx"