If you want to work it out, you need to read the note given to you when you make a particular choice :)
Viewing post in The Good People (Na Daoine Maithe) comments
It's near the beginning, if you're nosy when in the outpost you should get it. But I agree with Honeyypott, this isn't super accessible.
I used the link posted above by the dev to decode and I still couldn't do it as I had to bounce between 4 different pages (letter, password, decoding site, and somewhere to type it initially). I had 2 different potential options as some letters has 2 different options (like y or h), and I still couldn't get it.
It began hurting my eyes and triggering migraine (I get chronic migraines so this is a risk any time I do anything, especially which involves going from light to dark screens regularly), so for me this genuinely isn't disabled accessible at this moment.
Maybe in the future there'll be another way to manage this.
I love puzzles but ones that require lots of faffing about between different pages where some are bright and some are dark is very difficult.