TL;DR — at age 14, Peter Capaldi was so miffed that another teenager had been appointed by the BBC to run Official Doctor Who Fan Club, he ran a one man letter writing campaign to take over the post and club himself.
An analog era keyboard warrior, Capaldi sounds like he was a bit of a pest in his teens. The appointed Fan Club coordinator, Keith Miller, recalls that Capaldi "haunted my time running the fan club, as he was quite indignant he wasn’t considered for the post."
The linked 2013 article has some letters from show producer Barry Letts' secretary, Sarah Newman to Miller that reflects this portrayal of the Who star as a young pup. Miller ends by quoting a phone call with Sarah Newman following the "exterminated by Daleks" letter:
I asked how things were going with Peter Capaldi. ’Oh god, I wish someone would sort him out.’ Then she paused. ‘Actually, he lives in Scotland too – could you pop over to Glasgow and sort him out for me?’
By all accounts Capaldi was fairly terrible back then, but fortunately he channelled that deep fandom and knowledge of the show rather more constructively into one of the most layered and complex renditions of the Doctor that has graced the screen.
Old enough to have heard some of the scrattle in real time - some of the most annoying young fans are now the ones responsible for the best of the new series, so, yannow, suckit.