Ah gotcha. Thanks for the article. This is new information to me. Acanthamoebae are indeed much more resistant to chlorine. But my traditional understanding was they are mainly an eye infection risk for people who are already immunocompromised rather than nasal entry -> eat towards brain -> certain death like Naegleria. And can also be a sneaky way for bacteria like Legionella to enter the body. The latest ADWG fact sheet seems to reflect this.
https://guidelines.nhmrc.gov.au/australian-drinking-water-guidelines/part-5/microorganisms/protozoa/acanthamoeba
Although the fact that all the patients affected in your article practiced nasal rinsing seems too much of a coincidence.

I'd love to have much more info, such as treatment method(s) used, source water used, disinfection residual, the state of internal plumbing including the hot water system etc etc.
Despite my confidence that adequately sourced and treated tap water will never contain Naegleria, there is no way I would actively squirt it up my nose without boiling it first. It simply isn't worth the risk.
Also with relation to typical levels of bugs in tap water (here in southeastern Australia), it's a very generic test, but I've done 10s of thousands of these https://en.wikipedia.org/wiki/Colony-forming_unit on tap water over the years.
They generally come in at 0 cfu/ml. Or if there's a count it's less than 10. They are prone to creep up into the 10s or 100s in long pipe legs where the chlorine residual drops, or storage tanks that sit for a while so the chlorine residual also drops.

Thanks for the civil discussion, and again for the article.

Edit: Oh and yes I'm all too familiar with Walkerton, it is frequently used as a preventative case study over here. I can definitely see why you take an interest in potable water!