p4convert documentation needs to provide a "scary message index" with a description of what each of these messages mean, how it effects the quality of the conversion.
And what needs to be done because of it...
Many, Many users contact support with these questions.
Here's my current list of scary messages:
"... :Unmappable char set, storing file as-is"
"... SKIPPING: cannot delete a non-existant revision."
"... ... Non-unicode server, downgrading file to text"