Dan thinks I'm mistaken and provides the following evidence:
The Pluperfect of Completed Action. The Pluperfect is used of an action which was complete at a point of past time implied in the context. (Burton)The problem is not that Dan's evidence is bad, but that Dan doesn't understand the evidence.
The Pluperfect represents an action as already finished at some specified past time (Goodwin)
The pluperfect is a verb tense that indicates that something happened before time X, where time X is itself a specified (at least usually) past event. That's a bit like the future perfect: a tense that indicates that something will have happened before time X, where time X is itself a specified (at least usually) future event.
The ordaining in Acts 13:48 takes place prior to the specified hearing, being glad, rejoicing, and believing. That's what the pluperfect indicates. It was complete by that time, it was not performed at that time. It does not indicate that we can state when precisely the ordaining itself occurred. I would suggest that Dan contact a Greek professor who he knows and trusts to clarify this grammatical point to him, as he obviously doesn't trust me.
To provide a simple English example, the following sentence uses the pluperfect: "I had cleaned my room when my mother came home." In this example, "when my mother came home" is the specified time. It is not the time when the cleaning took place, but rather time before which the cleaning took place. I could have cleaned my room long before that event, or just before that event, but anyway when my mother came home, the room was clean.
The same goes for Acts 13:48. The ordaining was done before the specified time, such that at the specified time, the action of ordaining had already been completed. That's what Burton and Goodwin are trying to tell Dan, if only Dan would listen to them more carefully or to me. Hopefully, Dan will avail himself of someone whom he knows is familiar with Greek grammar: someone Dan trusts. That way, Dan can receive confirmation that what I am telling him is true, since it appears plain that Dan is not willing to take my word for it.