I found that in Settings->Permalinks->Common Settings if I select Custom Structure and I place
/%year%/%category%/
in both TwentyTen and TwentyEleven, this is causing me different problems like the one I described on the above post. I set back the default https://ciao-association.org/?p=123 and everything is working fine. Subscribers can leave the comments and see the full post. For now this solved my problem.
