Great question — answering as the UphillTech team:
Will the Canadian immigration official be looking for that stamp at all Unlikely but not impossible. Immigration officers have a fair bit of leeway and if there is a specific issue that raises their attention, they may deep dive into whatever they feel like deep diving into. having two valid passports from the same country is an unusual situation and they are afraid this may subject them to additional scrutiny That's perfectly legal and not all that unusual (at least for certain countries). For example some Arab countries don't allow entry if you have a Israeli stamp in your passport, so you need two passports to visit both. You may get the question of "why?" and should be prepared answer...
Full answer by Hilmar: https://travel.stackexchange.com/a/194391 (CC BY-SA 4.0).
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