The only time I've ever been upset about a thread being shut down was when Alsacien abused his MOD powers to lock the 'EU Financial Apocalypse' thread because he'd had his arrse handed to him repeatedly for about four months (though I wasn't as upset as Bokkatankie who got banned/flounced for his protests and for calling Alsacien a fascist cnut or somesuch). It was rather ungrateful of Alsacien because that thread founded the Economics Forum (which Arrse so clearly desperately needed because the posting rate in there is truly bewildering) and helped Alsacien up the greasy pole to Arrse MODship.
Beyond that, in over sixteen years, the only time I've mourned one of my threads was 'Dry Your Eyes Princess' -
though I freely accept that, had that continued, the entire membership of Arrse would have ended up in court or on a register, or both.
https://www.arrse.co.uk/community/threads/dry-your-eyes-princess.171242/