I don't think any person who understands more about multisig wallets will have a second doubt about it, because it is a perfect match for what we may need to know or do when it comes to wallet security; some may not know its relevance because they have little knowledge or idea about Bitcoin wallets and security measures. A wallet that supports two-factor authentication security measures should not be taken for granted.

Come on, you can't really say this. What about the possibility that your single-sig entropy was not generated randomly, as with the Coldcard case? Or what if your passphrase is not secure enough, and can be brute forced by someone finding your seed phrase? Or what about the idea that a strong passphrase is not human readable, and you can make a mistake by choosing to write it down? (As opposed to another seed phrase.)

This is far from a good idea. There are many people who have come up with splitting their seed phrase in 2 or 3 parts so it is "divided" too. This is just nonsense, you will get yourself locked out.

If you have a large amount of assets, then you might consider using multisig.. but if not, I guess it's not necessary to go that far.. the most important thing is that you understand what you're doing and can properly secure your Bitcoin, that should be safe enough.. because multisig requires some setup before it works, and if you make a mistake in creating it, you'll only make things harder for yourself.

I don’t deny that, and I completely agree with you regarding this point. Earlier, I mentioned that multisign wallets require a fairly strong memory.
Multisign wallets are great to use, but in my own experience so far, I haven’t needed one because I’ve been able to get by with a single-signature wallet. What I mean here is not that you have to remember every letter and word of the seed phrase, but rather where it’s stored.

It's about security, how you keep your devices clean and secure, how you create and use your wallet rightly, safely and securely, then how you store your wallet backups securely too.

All these things must be practiced with good carefulness, and only knowledge about security won't be enough to help you, your devices, wallets and funds. Practice matters at the end and will decide whether you secure your bitcoins successfully or lose it to hackers or bad people.

So multisig wallets won't be enough if you are careless.

Privacy also matters as if you don't let anyone online or offline knows about your Bitcoin wallets and bitcoin funds, you will not become a target for a hack or physical attack.

Multisig wallets will require a little bit more transaction fees.

Quantum computing power will be incredibly expensive during the first years it will be available, and it will also take weeks or months to derive a single key. In this case, if you have two addresses with 1 BTC on them, and one is a multisig address, then the hacker will for sure first try the single address.

Once this "first post Q-day phase" is over and quantum hacking has been confirmed, I guess nobody will re-use an address anymore and post-quantum cryptography will be implemented. So this is a mechanism to increase the likelihood that you will not be a target in the first post-Q-day phase.

I don't understand the point of these examples ... these things can happen with any kind of key, not only with multisig, I guess the probability to mess this up is the same.

If you're worried about a key generation algorithm (?) you could generate two HD seeds and then use one of the derived addresses each.

(BTW, I meant passphrase in the sense of "seed phrase" and not some random "password" or so. I'll change this in the other post to the correct wording.)

Okay. What if we have two addresses and the multisig type contains 10 BTC whereas the other address that is not multisig contains 1 BTC, which one do you think the attacker will go for? Personally, I feel he will likely go for the address with more BTC (In this case the multisig address).

I think everything here is tied around the amount of BTC in question. Let's assume one quantum computer is worth 0.5 BTC, the profit the attacker will get from attacking the other address will be 0.5 BTC (1 BTC - 0.5 BTC). Now if the same attacker uses two quantum computers to attack the multisig address type, then his profit should be 9 BTC [(10 BTC - (0.5 + 0.5) BTC]. So If I am the attacker I will definitely attack the multisig despite the resources I'll have to spend, because at the end of the day I'll gain more.

Assuming that you know how to create the multi sig wallet safely.

The need for a multi-sig wallet depends on how much is in your personal holding, having a secure multi-sig wallet to keep 0.0001BTC is just an overkill and no necessary in my opinion. But if you have a couple dozens or even higher then scatter it around on multiple sig wallet to reduce the risk of losing.

You know that over-securing your assets can sometimes be a problem for yourself. If you only hold a few hundred dollars worth of Bitcoin, I think there's no need for multisig. Multisig is usually for advanced use – for example, when you hold millions of dollars worth of Bitcoin, maybe you can consider this option. For regular use, I think a simpler setup with a hardware wallet is enough.