I thought we were only allowed to add bug fixes but I've seen others making changes like adding an "easy mode" after the submission deadline. 
I've had some feedback and adding an easy/story mode to my game might help more people make it to the end. (I totally understand that choosing metaphor over "fun" might discourage some people from persevering with my game when there are nearly a thousand other games to play)

That is what I was under the impression of. I know I have to make gameplay tweaks and balances but I figure I would do it after voting ends in the spirit of the jam.

Same here, there are a few bugs people have pointed out but I feel I should wait till the rating is done before I fix them.

The FAQ says: "You can fix game breaking bugs in your submission and upload those. If your game is unpleasant or unplayable due to technical issues, we want you to fix those! You just cant add new features or gameplay. or things like that."

Based on the FAQ I would understand the rules like this:

1. Bug fixes are explicitly allowed. Players should be able to play the game from start to finish without experiencing problems that prevent them from continuing the game as intended.
2. Editing the itch.io page: adding screenshots/videos, adding/changing text in the game descriptions is allowed.
3. Small adjustments to the game are okay if they are done in good spirit and for the same reasons than in 1)
4. Additional content (like new levels, puzzles, abilities, enemies), changes to game mechanics/balancing or replacing graphic/sound assets with new ones is not allowed.

I have fixed some bugs / add work arounds to them to guarantee that the game is fully playable. For example: adding a level restart button to give the player a way to recover from some serious bugs (like player character randomly not spawning at the start of the level) and fixing ground check to allow the character to jump when they should be able to & to prevent the character to get stuck in certain situation. In my understanding the rules clearly allow both of these changes. Alongside the last bug fix just today I also changed some jump parameters to make some jumps (that were meant to possible) easier because some players had had a lot troubles with jumping. This might have been in the gray area but because it was usability thing and really small/quick change I believe it's not against the sprit of the jam.

Changes that I would like to do but have not done yet because they should not be allowed during rating period include: editing the levels themselves (neither gameplay reasons or moving misplaced sprites that only affect visually), creating new levels with more mechanics, changing the main mechanic (for example by adding a possibility for player to optionally fast-forward time to make some waiting times shorter), adding a script to have background music to be cut when the game ends to signify the moment of character's death