With sufficient reputation (2000), one can make changes to any post on Stack Overflow without review or reward - no longer does one get reputation from having an edit approved.
Those who subscribe to the "the information in this post should be available to everyone in the most readable way" will make changes to curate the material. Reading a post where the wrong 'their' or 'they're' or 'there' is used by someone can be very distracting and these edits serve to make that post more useful to more people as well as helping the OP become more proficient at English through correction.
Its not for the reputation (which they don't get) but rather the "this is good, but can be better" and trying to make Stack Overflow the best place it can be.
Those who subscribe to the "the information in this post should be available to everyone in the most readable way" will make changes to curate the material. Reading a post where the wrong 'their' or 'they're' or 'there' is used by someone can be very distracting and these edits serve to make that post more useful to more people as well as helping the OP become more proficient at English through correction.
Its not for the reputation (which they don't get) but rather the "this is good, but can be better" and trying to make Stack Overflow the best place it can be.