I saw on the ruling for Blaze Commando that it only triggers once even if the spell damages multiple things. Does Syr Carah, the Bold work the same way? She is worded slightly differently, so I was wondering if the distinction matters in the same way that "becomes blocked" and "becomes blocked by a creature" mean different things, such as with Drelnoch versus Infiltration Lens.
Syr Carah's first ability triggers each time "Syr Carah, the Bold" or "an instant or sorcery spell you control" deals damage to "a player" (C.R. 603.2, especially C.R. 603.2c; for the use of the indefinite article a or an here, see this thread). For example, if the same instant or sorcery spell "you control" deals damage at the same time to one or more players, that ability triggers once for each such player. Compare that ability with that of Sun-Crowned Hunters ("Whenever Sun-Crowned Hunters is dealt damage, ..."), which triggers only once each time Sun-Crowned Hunters is dealt damage, no matter how much damage that is or how many sources deal that damage to Sun-Crowned Hunters at once. See also C.R. 700.1, this thread, and this thread.
Does Syr Carah trigger multiple times when a spell hits multiple players?