The symbol used for open doors and windows

Looking on the wiki here and here, it appears as if the symbol for open doors and windows used to be a slash \ character, but in my game it’s instead represented by a single quote '. Also windows were blue in the wiki picture? Can someone please confirm that this is actually the default behavior and I didn’t somehow modify it myself? I honestly prefer having it as a slash \ and it seems to make more sense (imo) so I really wonder why it changed (if it did.)

The characters change by the versions. Plus the wiki is outdated and wrong in some places. So take what it says with a grain of salt.

You better look into the sources. Single quote (') is used for all open doors and windows, for example:

    "type": "terrain",
    "id": "t_door_o",
    "name": "open wood door",
    "description": "A standard wooden door that doesn't look very resilient.  It'd probably burn easily, too.  This one is wide open.",
"symbol": "'",

Why not use a tileset if the same character thing bothers you so much? Would simplify it. Might not be the same look you are going for though.

I don’t remember \ (backslash) ever being the open door/window character. I was going to say it’s always been the ’ (single quote), but then I decided to search the project history, and found that in the very first version of terrain.json, it was a " (double quote), likely due to automatic conversion:

        "name": "open wood door",
        "symbol": "\"",

I then went back to 0.1, looking for what it was in the very first release of DDA:

{"open wood door",  '\'', c_brown,   2, tr_null,

The same thing shows in Whales’s first ever commit to the Cataclysm (not DDA!) repo:

{"open wood door",  '\'', c_brown,   2,

I’m purely guessing, but I think the wiki page creator (whether a person or a bot) misunderstood the backslash. The backslash is escaping the " or ’ so they don’t close the string/char literal, i.e., so that you can have the literal quote character be part of the quoted thing.

But in any case, it’s really only ever been a quote mark. Maybe a mod could be made to override a terrain symbol?