Cos I thought we can only verify that a signature was signed by a public key. Cos otherwise everyone can decrypt the signature since public key is, well, public. This article and this both seem to say yes we can decrypt.
And this image from SO too -> https://i.sstatic.net/q28Zw.png
Could we technically decrypt a signed message using public key?
A signed message does not even need to be encrypted in the first place. Instead a message signature is a cryptographic hash over the message and this hash is then signed using a signature algorithm. Such signature algorithm might be like an encryption (in case of RSA) or something else (ECDSA).
Still, the original message cannot be restored from the hash and thus also not "decrypted" from the signature. Apart from that the message is encrypted TO the recipient while the signature is done BY the sender - different keys are involved here.
Cos otherwise everyone can decrypt the signature since public key is ...
Decrypting the signature is different from decrypting the message. As for the "decrypt" part - signature validation involves decrypting in case of RSA but with ECDSA and others it is different.
