Two GCC stories

You can do that with GPG. For people I know from the net but never met in real life I use "lsign" in the edit menu. Most frontends have a checkbox for this. Local signing means that you trust the key but you don't want to vouch for it in the public.

In any case it is entirely up to you how you do the suggested identity verification when you sign a key. It is your and only your personal policy.