I pretty frequently look through SE sites' Local Storage when debugging my own scripts. Every time I do, I'm faced with screens like this:

AutoReviewComments' keys are everywhere - there are about 60 of them for me (depends on how many auto-comments one has saved). It's not only annoying, it's also a pretty inelegant storage pattern. A better choice would be to use a single property instead. For example, rather than AutoReviewComments-commentcount, AutoReviewComments-WelcomeMessage, AutoReviewComments-desc-6, AutoReviewComments-name-6, AutoReviewComments-LastUpdateCheckDay, a single object could be used instead:

{
  welcomeMessage: 'some string',
  LastUpdateCheckDay: 12340000,
  templates: [
    {
      name: '[A] Answers just to say Thanks!',
      description: 'Please don\'t add "thanks" as answers. .....'
    },
    {
      name: '[Q] Some template name for question comment',
      description: 'Some description'
    },
    // ...
  ]
}

JSON.stringify can be used to save such an object in storage, and JSON.parse can turn the JSON string back into an object:

var db = JSON.parse(localStorage.AutoReviewCommentsSettings);

I would love if I could make a pull request to change AutoReviewComments' storage to the above structure. Would this be an acceptable change for me to work on?

This would still be completely backwards-compatible: the script can check to see if the individual AutoReviewComments keys exist, and if they do, they could be extracted to construct the new settings object. The modifications would still be able to read settings in either the individual format or consolidated format, but would only save settings to a single key.