I am also no expert, so speculation ahead. - I have heard that the DTCC does not require collateral (or perhaps not as much collateral) for the party selling t

I am also no expert, so speculation ahead. - I have heard that the DTCC does not require collateral (or perhaps not as much collateral) for the party selling the stock. This would mean that allowing selling would pose little to no risk to brokers. - If that's not true, I wonder if Robinhood decided that preventing people from closing positions was an unacceptable risk. If GME tanked and people couldn't sell, the outrage would be insane. So perhaps they did the math, realized that their available cash wasn't enough to support both buying and selling, and decided that only allowing sells was the least bad option available.