Namo Buddhaya!
Only to other monks.
As i see it, there is nothing inherently wrong with displaying miracles & revealing attainments, but there is a problem when people do this of evil desire/confusion.
Furthermore I think that it is important for the bhikkhusangha to be presented as united with minimal distinction as to fame & honor befalling particular bhikkhus in favor of others.
I also think that it makes a hard divide between monks and laity where monks do not get much entangled with lay yogis because now a monk can’t talk freely even if he would want to grow close.
It’s good for the monk and the layfolk are incentivized to go forth if they really want to know what their friend can declare of himself.