You can be banned for AFKing a strike if you set your controller upside down or use a rubber band (or any such device) to avoid idle detection. Their ban policy says one possible reason for a ban is:[quote]Using an external program or device to automate gameplay or circumvent idle detection[/quote]It also says you may not be fully banned from Destiny, but from the specific activity you were violating the policy in. (Aka banned from strikes, but you can still do raids/missions/crucible.)
My only question is how do you report it more specifically? The in-game reporting system doesn't have options for specific policy violations that should result in a ban/restriction.
[url=https://www.bungie.net/en/Help/Article/11929]Source[/url]
Last week I did the heroic and got booted because of connection as Priest was about to die. Started it again and finished. Then started dragon strike and got the priest so I wasn't best pleased but I don't ever quit on one. One guy though just AFK until the very last second ended with no kills and got invective! I was so pissed I took a screenshot!