Trying to avoid captcha, it’s a surefire way to prevent legitimate posting by a significant percentage.
We have had a total of 4 spammers so far, 95% of spam content got caught in the Akismet check that we use. I added a few words to the blacklist the other day and that seemed to increase the capture rate to 100%.
The spammers actually seem to have human help (non-bots) since they have to register for a ForgeRock ID account to get access to this forum. I’m slightly impressed.