I was a dual national for about 7 months after naturalising as an Australian. My original citizenship was Malaysian. Whilst I have no intention of pursuing a career in federal politics, I've never been a fan of dual nationality - I don't begrudge those who are dual nationals, I just feel uncomfortable myself being a dual national as citizenship to me is the ultimate statement of allegiance to a nation state and membership of a unique political community.
In any case Malaysia does not allow dual citizenship - this is in fact written in the Malaysian constitution itself. But they didn't make it easy to renounce Malaysian citizenship! When I rang the High Commission in Canberra, I pointed out a provision in their constitution that allows the government of Malaysia to unilaterally strip me of citizenship as I've become a dual national and exercised the entitlements of my Australian citizenship - so couldn't they just exercise their constitutional powers and spare me the rigmarole of going through the renunciation process? Long story short, turns out they're too incompetent to enforce their own nationality law and I had to actively apply and incur additional expenses to renounce Malaysian citizenship. The forms are in Malay which I don't understand - they provided a basic translation, and the biggest expense was probably getting a Notary Public to witness me signing the form as no one else would touch documents written in a foreign language. I wasn't confident that I'd filled in the form correctly so also provided a stat dec outlining the ways I have exercised my Australian citizenship (membership of a major political party, enrolling to vote, voting at a state election) and could they please enforce their own nationality law by unilaterally extinguishing my Malaysian citizenship anyway even if they find mistakes on the application form. Took about 7 months in the end before I got a letter - that assuming Google Translate hasn't gotten it all wrong - confirmed that I'm no longer Malaysian and thanking me for my service to the nation...
I suspect I wouldn't have been as motivated to renounce if I had a more practical 2nd citizenship or one of another like-minded Anglosphere state, but it actually felt liberating when the confirmation of renunciation arrived - probably almost as proud a day as when I officially became Aussie. It was also relatively easy for me compared to other people who tried to renounce Malaysian citizenship and got the runaround and being lectured by High Commission staff about "loyalty."
I suppose as a migrant things like your citizenship status is something I'm acutely aware of, probably more so than most. I'm always stunned by how little awareness people can have of their own legal / citizenship status and the implications for what it means for their rights, entitlements etc in any country - parliamentarians aside, the more garden variety usually consists of Brits who have lived here forever thinking they're citizens and subsequently inadvertently overstay or those who arrive here as kids but get into trouble with the law as adults and get deported to a country they barely know as they or their parents haven't been bothered enough to take out citizenship.
I do feel sorry for Larissa and Matt if he isn't lying (I think the Scott Ludlam situation is arguably a bit more dodgy) - as I do feel what happened to them is unfair and for Larissa she relied too much on her parents' own inaccurate understanding of Canadian citizenship law when she should have probably done more due diligence - not unlike a lot of accidental Americans trying to renounce US citizenship now, which they've never wanted, to avoid global taxation. I'd hope the High Court takes a more nuanced view of s44i going forward as quite clearly neither Larissa nor Matt sought or wanted Canadian/Italian citizenships let alone show signs of bearing allegiance to Canada or Italy.