Certificates do not by definition proof who is behind it. If you trust that 'source' is entirely up to you. This is why most 'secure' connections made with certificates are for confidentiality and integrity, but you still don't know who you are talking to. CAs do have rules that tell the certificate owners not to share the private key, but in practice that is very hard to check.
You can also go up the chain and say 'I don't know Coca Nuts Unicorns Ltd, but I do know the authority higher up the chain, Verisign for example.' If verisign is ok with it, maybe so are you? This is a slippery slope though, because CAs will hand you a certificate as long as you give them some money, some account info and a email address. You just can't be sure of who is behind that certificate.
There is a concept with certificates, extended validation, which does help you out there. The basics of that concept are that the owner had to get validated by the certificate authority.
An Extended Validation Certificate (EV) is a certificate used for HTTPS websites and software that proves the legal entity controlling the web site or software package. Obtaining an EV certificate requires verification of the requesting entity's identity by a certificate authority (CA). Web browsers show the verified legal identity prominently in their user interface, either before, or instead of, the domain name. During software installation, the verified legal identity is displayed to the user by the operating system (e.g., Microsoft Windows) before proceeding with the installation.