Really? I wonder which apps does...

ZoomMath is an example of a third party App that costs money.   http://www.zoommath.com/

I think they have, but I don't expect they'll ever take those bits of code out.  And even if they did - even if they released new OSes tomorrow that did away with all the old protection mechanisms - I'd still say it's worthwhile to remain compatible with the older OSes.  I mean, personally, I'm still using 2.30 on my 84+, and given the state of the newer OSes, I don't plan on upgrading that in the forseeable future.  I think both my 83+es are running 1.19 now, but I kept 1.14 for a very long time, for the sake of program compatibility.  I'm sure I'm not the only one.

The only problem with older 83+ OSes is that they have a different ASCII charmap I think, or something related to ASCII is different, and as result, certain games using some characters will only send on a calc running 1.15 or higher.

They are missing a few characters, namely ~@#$&`;\|_%. They were added to allow compatibility with the TI Keyboard. 1.16 also added a few characters, but they are rarely used. Some of them are the arrows, the … character and also ß, which is used in German.

Is it completely gone, or is it just replaced with a more normal token?

So I sent this to my calculator and tested it out on an Axe app, but it said the length was wrong and refused to sign it.