It's not just Square, and Microstrategy,
Their impact can both be positive, or negative. Being among the largest HODLers of Bitcoin, they should have the responsibility to help in the development of the Bitcoin economy, and in the aspect of Bitcoin education.
Interesting to see that more than 2% is held by these companies moreover if you reduce the bitcoin which is not in circulation or is completely lost
this percentage would go futher up this means that they will get some big power to manipulate the markets too. Moreover other companies who would now try to enter would consider this factor too. I think if more corporates become determined to buy bitcoin we definitely are going to see price skyrocketing. But for that companies would want volatility to be on the lower side because these companies won't be taking big risk with public money.
I won't bother about the markets. I believe as more Bitcoins go in the custody of a few powerful groups, Bitcoin would cease to be a permissionless, and censorship-resistant system.
Plus what are Square and Microstrategy doing to help user growth, and infrastructure development? Are they simply rent-seeking?