Gold frequently moves sharply when a central bank speaks and barely at all when it acts. That pattern follows from how markets incorporate information.
Expected decisions are already in the price
Interest rate markets publish continuously updated expectations of future policy, and other markets price against those expectations.
A decision that matches what was expected therefore contains no new information, and prices reflect it before the announcement is made.
What moves markets is the difference between what was expected and what occurs, which is why an unchanged decision can produce a violent reaction if it was not the one anticipated.
Gold responds to the real return on alternatives
Gold pays no interest, so its attractiveness depends on what interest bearing assets are offering after inflation is accounted for.
When expected real returns on those assets fall, the disadvantage of holding a non yielding metal narrows and demand for it strengthens.
Central bank communication moves both the nominal rate expectation and the inflation expectation, which is why it affects gold more directly than most commodities.
Guidance carries more information than the decision
Statements accompanying decisions describe how officials view conditions and what would cause them to act differently in future.
Because policy moves in a sequence rather than in isolation, information about the path matters more than the single step being announced.
Markets consequently parse changes in wording closely, and a modified phrase can move prices more than the decision it accompanies.
Currency effects arrive at the same moment
Policy expectations move exchange rates, and gold is quoted in dollars, so a single statement produces both a rate effect and a currency effect.
These sometimes reinforce each other and sometimes offset, which is why the immediate reaction can be smaller or larger than the news alone would suggest.
Untangling the two afterwards requires looking at the metal's price in several currencies rather than only in dollars.
Reserve buying is a separate channel
Monetary authorities are also buyers of gold for their own reserves, and that activity is reported with a delay rather than announced in advance.
It affects the market through actual purchases spread over time rather than through expectations, so it influences the trend more than any single day's price.
The two channels are easily confused, though one operates through what officials say about rates and the other through what they quietly buy.