Say things that aren't accurate or cannot be proven accurate unless the one who made an anonymous trade reveals it himself.  Saying that Mackie did not sell any shares yesterday could be misleading. Mackie being a profile investor may have used the cloak of anonymous to execute trades.

According to Investopeadia :

"What Is Anonymous Trading? Anonymous trading occurs when high profile investors execute trades that are visible in an order book but do not reveal their identity. While most traders trade non-anonymously, there are several reasons that larger traders prefer to keep their participation in a market a secret."