This is true when you are an active writer, anyway.
Yes you can --> change your signature.
Once you've changed the signature but you didn't post a new message, but anyone else replied to a thread that you were active sometime ago --> then your signature will be also captured.
And then, searching for expressions used in the signature these are on top of the results!
Now let's talk about the opposite:
a) you don't write articles and
b) nobody is replying to older threads.
In this case this one
seems to be arbitrary and is in need of an explanation.
Why pizza? Why pico?
