I'm reading Analysis of hashrate-based double-spending article. On page 10 there's a table listing probability of successful double-spend attack in relation to required number of confirmation.

Looking at hashrate distribution I can see that BTC.com now owns 20% of network hash-rate. Given the numbers in the table in the article, it makes me wonder whether there have been any publicly revealed double-spend attacks by BTC.com or other major pools. BTC.com now has roughly 20% chance of successful double-spend attack against merchants waiting for just 2 confirmations.

Are there any watchmen monitoring the nefarious activities of mining pools on Bitcoin network akin to Certificate Transparency which monitors certificate authorities in PKI?