Quote from The Big D:
This whole discussion seems to be wanting for an example of a working trend following system, so here's one:
On weekly bars the S&P has an upward bias in excess of basic returns when a given bar opens over the 40 bar EMA. It has a negative bias when a given bar opens below the 40EMA.
The statement I just made is easily verified, it's tradeable, it's highly statistically significant, and it's been that way for decades. It's classic trend following.
So to get down to brass tacks, in certain instruments on certain time frames there's ironclad evidence of trending even using a trivial detector for trends. Now discussing how best to find the right instruments and timeframes and how to best follow the trends thus discovered is a broad topic. But let's not pretend there are no statistically significant trending instruments out there.