But plenty of people have permanently damaged their knees by consistently running without getting advice on how best to do it.
You don't need a personal trainer for that. But asking someone "to tell me how to run" ain't a bad idea, even if it's a question on a running board on the Internet.
The people who read running boards all the time roll their eyes at stuff like this. Saying that running will hurt your knees is the running equivalent of "The GPL will infect your codebase." It's not true, but it sounds scary.
Usually, if you ask runners how to run, they will say something like, "It's not that complicated. Run more miles, slowly."
For example: https://www.reddit.com/r/running/comments/wi8zq/want_an_easy...
OTOH, "Runner's Knee" does seem to be a serious condition affecting a lot of people (much like "Fencer's Knee", which I'm more familiar with). From the same subreddit:
https://www.reddit.com/r/running/comments/3hx43k/how_i_cured... https://www.reddit.com/r/running/comments/26jaax/3_years_ago... https://www.reddit.com/r/running/comments/1gdw5l/can_i_fix_m...
And a number of people, when discussing the problem, reference bad technique as a causative factor.
However, you're absolutely right that it seems there's little evidence for permanent damage. I found this thread particularly interesting:
https://www.reddit.com/r/running/comments/1fehx2/wife_trying...