Bitcoin is risky so one should not invest in risky sector like Bitcoin with loan from bank. We know investing in Bitcoin requires long-term planning. Now if you take a loan from a bank you have to repay it within a certain period, but you may fail to repay the loan. However, I don't invest more money than I can afford to lose, I invest some money from my income, so why should I take a loan from a bank? You cannot guarantee 100% profit by investing in Bitcoin. So I think you should not invest by taking loan from bank.
If the person does not have a steady income then borrowing money from a bank will be dangerous, but if the borrower has a steady income then applies for a loan and invests it in bitcoin, it may not be so dangerous, why? because in my opinion the borrower will not have difficulty paying the debt plus interest so they are not too worried about their assets and if the price of bitcoin falls they only need to hold it for a long time until the desired price target is reached, I convey this with my assumption that the borrower wants to buy bitcoin directly without going through the DCA strategy or buying periodically, but if using the DCA strategy I also do not recommend borrowing from the bank.
Depends on the size of the loan, but you are right. I have taken loans all the time, and while none of that was to buy bitcoin, none of it was for making money reasons. Most of it was medical reasons and I did not made any money and then I worked and made some money and paid it back somehow, and I still have some loan and doing as well as I possibly could, that is what I am capable of doing at the moment.
So by same logic, if it wasn't for a medical reason, I could have gotten some loan, bought bitcoin with it, hold all my bitcoins and then pay the loan back just like how I paid right now with my salary. In that case, I would have made a lot more money but I would be afraid of doing something like that, even though I have already paid that much, if it was for bitcoin, then I understand being scared of it.