Lighthearted!
Ok so I've seen some corkers in the years I've been posting/lurking on MN. What's the worst advice you've ever seen on a thread? Here are a few (in no particular order):
Years ago, someone telling the OP to do all the housework and not give her four teenage children any simple chores to do because she was a single parent and they "needed to have a childhood" so couldn't possibly do the dishwasher or similar.
Someone on a pension thread telling the OP that her house was her pension, except she was renting and they hadn't read the OP properly.
Someone telling an OP without a car that going on holiday to the arse end of the Highlands to a tiny village was completely doable by public transport and encouraging her to go up there somehow and effectively get stranded in a village with no bus service or taxi companies.
Luckily on these sort of threads I also see a lot of people calling bullshit on the bad advice but it still makes me laugh and hope to God that the OP is sensible enough to listen to the majority (they usually are).