• macOS Monterey 12.6.1
• IINA v1.3.1

Expected behavior:
Keybinds to "#" (+ any combination of modifiers) for any valid function, inserted either via IINA's Key Binding GUI or via input.conf editing, should properly save and thereby continue to function after restarting IINA.

Actual behavior:
Functions keybind to "#" fail to work after IINA is restarted.
Keybinds for "#" are removed from IINA's Key Binding GUI list.

Steps to reproduce:
(Example)
Open Preferences, goto "Key Binding"
With a custom key bind set/file, use the "+" button to create a new Key Bind.
Record inputs "Shift+3"; "#" should appear in the recording.
Select action "Cycle", "Pause"

Test keybind with content.

Quit IINA.

Re-open IINA, resume playback.

Test "#" keybind again. Failure.
Open Preferences, goto "Key Binding"
Notice previously created keybind is gone.

• MPV does not have this problem.

Note, MPV documentation for input.conf instructs users to use "SHARP" when creating keybinds for "#". Editing IINA's input.conf, attempting to use "SHARP" to create keybinds also fails.

How often does this happen?
Every time, highly reproducable.

Thoughts
It's interesting that when creating Key Bindings to "#" using the GUI, they do immediately work. Even checking the corresponding input.conf, a seemingly valid line for the newly created key bind does show up; the above example creates "# cycle pause". However, I do think there is an underlying issue parsing "#".

I suggest implementing MPV's workaround, and using "SHARP" to create robust input.conf files.