During cryptocurrency transaction and when receiving cryptocurrency coins we do make use of the wallet address which known as a special identifier that provide location to receive coins and the issue new traders or not expert In cryptocurrency faces or might face is mistaking another alphabet or number for another or capital alphabet use in the place of a small alphabet in which each letter carries his own identification and using capital letter where to use Small letter might cause your transaction fail or you will not receive your fund.
And also the alphanumeric must be complete and no one should missed ,so it might not cause failure in your transaction.
So that is why is advised to copy and paste the wallet address and send to the sender of the coin and not typed.
Most addresses I've used are not case sensitive, so I believe one doesn't really have a problem with replacing a capital letter with a small one, though its not advisable to edit an address after copy pasting, if you notice any error after pasting an address you copied, it is best to recopy and paste the address than try to edit it, and like a user here said, Bitcoin addresses has a checksum feature which ensures that address pasted is correct and complete, Legacy addresses is the one most users have made mistake with since its the same with Litecoin address, but good thing is that this days, users no longer make the mistake of sending Litecoin to Bitcoin address and vice versa.
Where most newbies make the mistake of transferring or sending funds to the wrong address is when it comes to 0x addresses which is used across Ethereum, Binance smart chain, Polygon, Fusion, Avalanche, Heco, Okexchain, Cronos, Aurora, Cube Network, Arbitrum Etc.