Many readers have complained that their comments were blocked. I have complained repeatedly to WordPress, to no avail. The Happiness Engineers at WordPress (really!) proposed that you contact them directly for support:

https://akismet.com/contact/

They told me that I had a long list of banned words on my blacklist (e.g., porn, Nike [a regular spam item], etc.), that it might have stopped innocent comments. Like if you commented on your favorite porn or Nikes or clock parts.

I have eliminated the blacklist altogether, so now the onus is on them to find out why some comments never get posted.