This is definitely something Drafts is well-suited to helping you with…I would say a few things:
First, you can just use Drafts for this by opening the app and typing your comment without further action. Drafts are always stored with location (assuming you have granted location permissions) and timestamps for creation date/time, etc.
If you want them exported to file, then you can create an action to create the file. Drafts has action steps for most of the popular file services - like iCloud Drive, Dropbox, Google Drive, Box, OneDrive. These action steps can be configured to control the folder, filename and content in the file that is created when they are run (or, alternately append/prepend to existing files, if you would rather keep a running journal in a single file).
You can start by editing/duplicating one of the example actions for these services which ship with the app in the “Basic” action group, and modify it to suit your needs. Content, filename and other fields are configured using templates which combine text with template tags provided by Drafts to insert information when the action is run. The using templates article is a great place to get familiar with template and how you would use them to insert location, date or other information in the file you export.