While I second James' answer, I just want to share my personal experience: I lurk most of the SE communities here, and I am registered only in a small subset of them.
However, when I stumble into a post which can clearly benefit from an edit (think of the usual they're/their/there misuse) I don't really feel compelled to register and edit.
Since I can use the "improve this question" feature, I do it (screenshot below taken from a HNT).
[![example of feature: improve this question][1]][1]
Of course I am aware that I will never receive any feedback nor reputation for my edit, I just want to do my little part to improve this place.
It would be really odd if, while I am on vacation in a foreign country, I would be scolded for collecting an empty soda can thrown on the grass to dispose of it in the garbage bin. [1]: https://i.sstatic.net/i71DX.png