He mentioned Sieve in passing, I wonder what the problem with it is. I use Dovecot and Sieve, and have never had a single problem, apart from mis-written sieve

He mentioned Sieve in passing, I wonder what the problem with it is. I use Dovecot and Sieve, and have never had a single problem, apart from mis-written sieve rules. The syntax isn't the most concise, but how much worse could it be compared to a hand-rolled sorting program?