Why do you think I would do that? Even if I were a top Bitcoin programmer, that would defy my own personal principle. I have already spent a lot of my own personal efforts and (some) money to support Bitcoin network since version 0.9.x as I like the idea and the objective. I hate the change of its name to "Bitcoin Core" though, just because of some stupid people tried to disrupt it.

I believe this would only happen on a crappy in-house developed software and only maintained by 1 or 2 programmers. There are a lot of companies involve as this becomes an industry with huge market valuation and supported by thousands of developers around the globe. So I really doubt that we (including me) are so stupid to trust software that has no mechanism to maintain the integrity of the database.

What I asked in this topic is how to do manual check which is better and faster than using "bitcoin-cli verifychain" command. Maybe there is no other way to do manual check. But I believe there must be a mechanism within bitcoind (and bitcoin-qt) software to make sure the integrity of blockchain data is properly maintained. I asked about that mechanism is for me to understand the impact on my full node. A few years back when the blockchain data on my full node was corrupted, I had to do reindex resulting it to re-download the entire blocks from blk00000.dat.

But you pointed out something that I have to double check myself. I think I will intentionally corrupt the 2nd last blk*.dat file and run my full node on Bitcoin testnet to see what will happen.