2. It can leave one open to niche attacks and one becomes vulnerable to these cyber thieves who will extract private keys from signatures after a transaction has been made.
This is not actually possible. Many people frequently reuse addresses, including businesses that hold billions of dollars worth of coin.
3. Quantum computers could extract private keys if these addresses are re used.
QC may allow for the private keys to be calculated from
Citing an instance of the Ronin network incidence in March, where $540m worth of cryptocurrency was carted away by thieves hopefully by finding a collision of randomly picked message digest of 2¹³⁰+1 input of hashes causing possible collides by examining the square root of the number of possible output. Making re-use of Bitcoin addresses risky considering the chances of possible collisions even though the entire process might be time consuming hackers might choose to patiently wait till a collision is found just like the case of Ronin network..
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