Is this predicated upon installing and using Amethyst or ditto? So if you do not have these clients installed there is no issue is that correct??

Address reuse is not only bad for the privacy of the whole network but also reused addresses will be an easy target for (in case they come) quantum computers as the public key has been exposed in a previous transaction. It’s already implemented? That I did not realize. I thought it’s a discussion for now.

Amethyst and Ditto have indeed implemented it already.

It is actually always an issue since if you get these onchain zaps, you are in possession of these coins and your nsec is the private key to these coins. Nostr keys are generated the same way Bitcoin Taproot addresses are generated. Amd everyone can see that you have these coins and how you spend them.