Interesting articles. The specific issue of "black, “grey”, and “white” UTXOs is something to keep an eye on to see how it progresses. Whether it becomes a significant issue of regulation or not it’s still in the best interest of exchanges to blacklist scam funds. Opt-in privacy features like CoinJoin do have a stigma associated with them (this is touched on the Privacy course) as they can viewed as only people “having something to hide” use them.
I think the real question is whether these issues become a big enough problem for the majority of users. From the article, the “black” scam/hacked coins make up 2%, these are certainly a problem but not for most users as exchanges should already have blacklisted these. Grey coins are 40%, this could be a problem if exchanges stop accepting them. Ultimately though, if this becomes a real nuisance, then I think a privacy by default solution will become a priority for the developers. Then all coins become grey. MimbleWimble is step in the right direction.
The other point to consider is the narrative of BTC as “digital gold” vs “medium of exchange”. Most people would rather hodl their BTC than spend it. BTC is a horrible medium of exchange due to it’s volatility, but it’s an excellent long term store of value. Stablecoins are the de facto medium of exchange token in the current market and for the foreseeable future.
I’d be interested to hear what @Grant_Hawkins perspective is on this. He’s the instructor of the Privacy Course.