[Kranar]

You're misunderstanding the default behavior which is fine becaue it's commonly misunderstood and discussed. At any rate signature verification is not skipped by default, what assumevalid skips is script verification. Everything else including UXTO, proof of work, the transactions themselves, are validated.

[dlubarov]

That seems a bit pedantic; the client itself prints

> Assuming ancestors of block %s have valid signatures.

when using -assumevalid. I agree it's imprecise, but it's not exactly wrong, since skipping scripts implies skipping signatures.