These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Deconstruction: Last Year's Model does this in several ways. Firstly, we find out that the person Barnaby arrested might in fact be innocent of the crime. Secondly, a large portion of the episode is courtroom drama focusing on a murder that occurred months ago. Finally, the gambit they use to trap the real murderer is both extremely risky and almost fails.
Memetic Mutation - Not internet, but a running gag in general British popular culture; while Inspector Morse was already joked about for the sheer numbers of murders in a medium-sized city like Oxford, this show takes it to even more ludicrous levels in the rural setting.
Given a hilarious Lampshade Hanging in episode 3 or season 9, where Barnaby asks about a death and is told that it was natural causes, "surprising as it may be in Midsomer".
Queen Elizabeth II of the UK herself has actually asked (of the producer, Brian True-May, at the opening of a studio): "Why does anybody move to Midsomer anymore? They're just going to get murdered."
Note that Midsomer is actually a county, not a village as it is often misreported (perhaps understandably, since the same two policeman seem to be responsible for every single town and village within it), though many of the villages (especially in the earlier episodes) still have ludicrous enough murder rates in their own rights to qualify. Never mind wondering why anyone lives there; wonder why there is anyone left alive.
According to a Radio Times feature on the show, there were no less than 239 murders (plus 11 suicides, 11 accidental deaths and only 7 deaths by natural causes) over its 14 series—making it about 17.1 homicides per series and 2.7 per episode. If each season corresponds to a year, then Midsomer's murder level is roughly 1/6 of that of London (pop. 8 million). The Third Estate blog assumed that Midsomer has roughly the population of the rural county of Somerset and each episode covers a typical week (meaning about 140 people die a year); that would give Midsomer a murder rate of 17-per-100 000, 12-times higher than the UK average, with only 5 countries in the world having a higher murder rate per capita.
Narm: "Screw you, grandma!" ("Days of Misrule", series 11)