1 letter error. When you set the ownership of a room to the player while items link is active. Confusingly, this only occurs when item links is enabled.

Can you give more details. Do you get an error message (check the console with F12)? What exactly happens?

I have to say that ownership was coded with a view to being used with items not rooms, so that may well be the root cause.

Super late update because I had to deal with school stuff.

Basically, when dealing with item links and rooms, the room becomes clickable (which is fine by me, I like links) but the name is no longer capitalized. This includes the pronoun "Your", so room names become "your room" instead of "Your room", or "Lara" becomes "lara".

(Note that I do capitalize the names of my characters.)
It gets weirder. When I put an alias for them, it fixes the character (because I capitalize aliases) but not the player, because the player becomes "your".

My research tells me it's because, somewhere along the line, it calls settings.nametransformer, which only takes the alias, so while a capitalized alias of a character works, "your" is from possAdj, which isn't capitalized.

TL;Dr
Item links remove capitalization for room names.

How are you getting links for room names? I am trying to recreate your issue, but my rooms do not have links!

https://ibb.co/yqt1NjW

The Link above is the image (from Img BB, image hosting website) but I will explain it here.

Put the item links library in.
Set the room's owner as "me" (so like right below lounge, put owner: "me' or whatever you named the player) and the name of the room becomes "your room"

It's lowercase with links but uppercase without links.

The simple solution, to stop the link, do this in settings.js.

settings.getDefaultRoomHeading = function(item) {
  return sentenceCase(lang.addDefiniteArticle(item, {ignorePossessive:true}) + item.alias)
},

I will look at other solutions, as this does raise issues...

I have uploaded some new file versions. There were a few issues behind it, the biggest being the capitalisation failed if the string starts with HTML.

The commit is here for more details.
https://github.com/ThePix/QuestJS/commit/c2aac32416a0690c6337a384ebf269e1f6a48e69

options.noLink causes undefined error for non-room items, including the player.

https://ibb.co/ZWSbcR5

Oops, needs a deault options on line 256

settings.nameTransformer = function(alias, obj, options = {}) {

I have uploaded a new version to gitHub