Does Teferi's Ageless Insight replace drawing one card with drawing two, and does that interact with 'whenever you draw' triggers?

Teferi's Ageless Insight has a replacement effect (CR 614.1): 'If you would draw a card, instead draw two cards.' This means every time you would draw a single card, the event is replaced before it happens — you never draw one card; you draw two instead.

Crucially, the replacement produces two separate draw events, not one draw of two cards. Under CR 121.2, drawing two cards means performing the draw action twice. This matters enormously for triggered abilities that watch for draws, such as those that say 'whenever you draw a card' — each of the two draws is its own event, so the trigger fires twice per original draw (CR 603.2).

Teferi's Ageless Insight's own replacement effect does NOT apply to itself recursively. The two replacement draws are already the result of applying the effect, so they are not subject to being replaced again by the same Insight (CR 614.5 — a replacement effect can only be applied once to a given event).

Example: You control Teferi's Ageless Insight and Ominous Seas (which triggers 'whenever you draw a card, put a foreshadow counter on Ominous Seas'). You play Opt and scry, then draw one card. Insight replaces that draw with drawing two cards. Ominous Seas triggers twice — once for each draw — placing two foreshadow counters total.

If you control multiple copies of Teferi's Ageless Insight, you choose which replacement effect to apply first (CR 616.1). Applying one Insight replaces the single draw with two draws; you may then apply the second Insight to one of those draws, replacing it with two more, resulting in three draws total from the original one.