Warren Buffett has been a net seller of stocks over the past eight quarters, building Berkshire Hathaway's cash reserves to its highest-ever level. He's completely exited some positions, like Floor & Decor, and trimmed down positions in others, like Apple. Apple still accounts for the largest position in the equity portfolio, and Buffett recently said that he would never sell it completely. Selling some of its stock doesn't look like a loss of confidence in the company.Is it the same situation with Nu Holdi ...