It's crowded when you're finger tips to toes or you smash into the oncoming swimmer off the wall (the ones following you) which is typically the mistake of the one turning and not the oncoming swimmer but not always. You try to stick to lanes moving at your preferred pace. It's a little like driving - sometimes you get your own lane and sometimes you don't.
You haz kwestuns we haz anserz
Customs vary by when and where you learn them, and it’s feels very hostile, especially for casual swimmers. (In my online experience, the closest thing is the “eternal summer” phenomena in Usenet in olden times)
In any case, worrying about the nonexistent risk of swimming in a recreational pool is counter-productive — casual swimmers will be turned off by the experienced ones.
It'd also be a shock to me to see a second person just simply joining me in my lane. Is there a protocol for joining a lane other than, I guess, flagging me down and asking? Do people normally know how to accept having a second person in their lane?
Funny thing to be asking so many questions about...