The Cleric gains an ability (1 to 3 uses depending on level) to gain a one-off untyped bonus to some types of rolls. No action type is listed but I'd assume it is probably a Free Action.
A level 15 Scroll Scholar gets two uses of this ability. What if they wanted to use it twice on a single roll? It is an untyped bonus so it should stack, and it only takes a free action (I assumed) to do, so why not do it twice?
'cause bonuses from the same source never stack.
That sounds familiar. Where does it actually say that?
The only rule I explicitly remember is that bonuses of the same type never stack.
One might reasonably think that Flash of Insight gives an Insight bonus, but as written it does not.
Oddly enough, it's hidden in the Magic section of the basic rules:
Usually, a bonus has a type that indicates how the spell grants the bonus. The important aspect of bonus types is that two bonuses of the same type don't generally stack. With the exception of dodge bonuses, most circumstance bonuses, and racial bonuses, only the better bonus of a given type works (see Combining Magical Effects). The same principle applies to penalties—a character taking two or more penalties of the same type applies only the worst one, although most penalties have no type and thus always stack. Bonuses without a type always stack, unless they are from the same source.
(emphasis mine)
Ah, that does indeed look familiar.
I agree it is odd that it is hidden there, not under the entry for "stacking" or something like that.