I'm testing Komento on an existing website which already uses reCaptcha for public article postings.
When a user tries to post a comment the message, "Invalid domain for site key" is shown and Captcha is disabled.
I'm using the same keys for both and the domain has been included in reCaptcha configuration. The one difference I noticed is that on reCaptcha there are "site key" and "Secret key", whilst in Komento there are "Public key" and "Private key". This might be just nomenclature or go deeper.