https://github.com/ethereum/go-ethereum/issues/18405

That’s generally fine. The way clique works is that the in-turn sealer who should ideally sign next tries to sign and propagate the block immediately when the timer ticks. If no in-turn block appears within 500ms, the other signers start potentially creating alternative blocks (with random delays), this ensures that even if a signer is missing, the chain progresses more or less properly.

Now, if the original in-turn signer does come around and publish its block with some delay, that might reorg out alternative blocks signer by out-of-turn signers. At that point those will complain that their block was lost. The scary smiley is mostly meant for ethash :) Clique blocks have no subsidy anyway :)