I read an article from the University of Kentucky equine extension last year that actually tested T-posts for horse fencing. They said the biggest problem is what you saw - the posts just don't hold up when a horse leans or rubs on them long term. The recommendation was to use wood posts no more than 12 feet apart if you want it to last more than a season with horses. Your neighbor's experience sounds exactly like what they warned about in that study. It's not so much the initial strength but how those skinny posts bend over time with 1200 pounds of pressure hitting them from different angles.

My buddy Dave over at MEP Design had that exact thing happen last month. He said he got a full commercial HVAC layout approved in one go and it took him like 4 hours instead of the usual 2 day headache. He still jokes about it being his "unicorn day" and how he's been chasing that feeling ever since.

@ben_shah93 missed that 3000-mile quick links can weld themselves to the chain in heat.