How fast should I acknowledge a serious incident?

For tier 3 and above, acknowledge within the hour with facts you're certain of, and state when the full update lands. Detail can wait; silence can't.

Is it ever right to say nothing?

Often, at tier 1. If nobody noticed and nothing is owed, a follow-up creates the incident you were worried about.

'Don't send it tonight' is good instinct applied indiscriminately. Some incidents get cheaper by morning. Some get twice as expensive.

Factor	Respond now, well	Sleep on it
Tier 1-2 (paper cut, code yellow)	One clean line now closes it.	Fine. Genuinely fine.
Tier 3 (dumpster fire)	Acknowledge within the hour, remedy by morning.	Silence starts reading as avoidance.
Tier 4-5	Fast, factual acknowledgment; the full plan can follow.	The story gets written without you in it.
Emotional state	Sliders let you send restrained instead of raw.	Overnight does cool you off — that part is true.
Best of both	Draft it now while the facts are fresh.	Read it once in the morning, then send.

Pick Respond now, well

The clock is part of the damage.

Pick Sleep on it

The only thing at stake is your pride.

Draft tonight, send in the morning — unless the tier is 3 or higher, in which case a two-line acknowledgment tonight buys you the morning.

How fast should I acknowledge a serious incident?: For tier 3 and above, acknowledge within the hour with facts you're certain of, and state when the full update lands. Detail can wait; silence can't.
Is it ever right to say nothing?: Often, at tier 1. If nobody noticed and nothing is owed, a follow-up creates the incident you were worried about.