Really Simple CAPTCHA works poorly with WP Super Cache

In the Settings page for WP Super Cache, you can go to the Advanced Tab.
Somewhere halfway that page you can add pages which should not be cached. You can add the title of your page there, and save that string.
Here my testarea contents look like this:

wp-.*\.php
index\.php
guestbook

Then delete the cache that you have.
In my testing that will refresh each CAPTCHA on a page request.

Yes, I know about this workaround. I even use this setting for some pages already. Yet I would like to keep the guestbook page being cached for faster response. Now I have switched to user anti-spam question. Though it works fine, yet I consider CAPTCHA to be more reliable method (static anti-spam question can’t protect against automated flooding attack which is intentionally targeted to your site).

Thus with Really Simple CAPTCHA I have to choose between caching and using CAPTCHA. With reCAPTCHA I didn’t have to.

I understand that caching is hard to combine with this Captcha.
Looking at the plugin, it seems to keep its files for 60 minutes. You could consider having caches cleaned after 60 minutes in WP Super Cache.

reCAPTCHA has other problems however.
– It uses an external service, which I prefer not to.
– It gives problems for some people. It’s probably a server setting where they cannot connect to the reCAPTCHA service and just get a timeout. But it is quite annoying and confusing.

Yes, I surely see your reasons. I have already seen support topics where people complained their reCAPTCHA not working.

Thus may be it can be a good idea – to give them the choice of two options with proper warnings about each?

If you still consider returning of reCAPTCHA unacceptable, then it seems to be a good idea to add a proper warning for users. Something like this: “WARNING: CAPTCHA may work with errors inside cached pages. If you use any caching plugin then it is strongly recommended to disable caching for your guestbook page.”

Okay, I added a notice like that.
Thanks.