If people really want to hide their builds, then they can take the pitiful route of unequipping their gear before they log out - but the killboard armoury bypassing the hide inspection feature is a good thing imo.
The barrier to entry in RoR is already mega high, and lack of reliable information on good builds and gear setups is very common. I remember when I first started this game on my Engi and was trying to figure out wtf I was doing, and almost every good Engineer player I inspected had their gear hidden and ignored my PMs asking for gear advice, and most of the well meaning Engineer players that were willing to help me had (respectfully) no clue about quite a lot of things that they were very confident about and would have sent me in the wrong direction entirely - I'm glad new players now don't have that same issue, or at the very least that it's not as bad.
Also, RE: KDAs and the killboard, I see no real reason that players shouldn't be allowed to hide their deaths if they want to. If it helps them enjoy the game more and they don't like the fact that the killboard is tracking all of their deaths, then it seems like a good feature to me. I can see this turning into an issue with tracking other peoples kills, but I'm sure there's a solution in there that can work for everyone