There is a long thread with people claiming a GM told them doing Court of Seregost at 105 tier 2 and triggering the challenge to get the extra chest is an exploit and they could be banned:
https://www.lotro.com/forums/showthread.php?662071-105-Court-of-Seregost-Killnet-chest-now-banable
There has been no official statement about it, just a lot of random comments by players.
Running it twice at 105 tier 1 and tier 2 without the challenge to get both the silver and gold chests it OK.