Jews have always considered God's name unspeakable and never said it aloud

This claim is usually offered as a fixed, timeless Jewish practice, but Heiser draws a clear line between two different periods. In the Old Testament period itself, God's name was spoken constantly, and not quietly. Exodus 3:13-15 has God commanding Moses to use the name explicitly when the Israelites ask who sent him. Numbers 6:22-27, the Priestly Blessing, has Aaron told to speak the name aloud, three times, over the whole nation; not written down and handed out, but spoken: "The LORD bless you and keep you; the LORD make his face shine upon you…"

The reluctance to pronounce the name shows up later, specifically in the Second Temple period, which happens to be John's own era, the time Revelation was written. And even then it wasn't one uniform rule. The Dead Sea Scrolls show several strategies: some texts write the name out plainly, others replace it with four dots, others mark it with dots above or below. Aramaic-speaking Jews typically substituted "Mar" ("Lord"). The Greek Septuagint mostly used kyrios ("Lord"), though some manuscripts transliterate the Hebrew letters oddly into Greek capitals that visually mimic the Hebrew. And the first-century Jewish writer Philo used ho on ("the One Who Is," straight out of the Greek of Exodus 3:14) as a divine name at least eight times without anyone calling it blasphemy.

That last detail matters for Revelation specifically: John opens the book with a divine title built directly off that same Greek phrase from Exodus 3:14, "him who is and who was and who is to come" (Revelation 1:4, 1:8), which is exactly the acceptable, literary way of voicing the name that Philo also used. So the honest version of this claim is really two claims stacked together: the Old Testament norm was to say the name, and the reticence that eventually became standard Jewish practice is a real but later development: one Revelation's own opening verse is actually working with, not avoiding.