For me right now (Firefox on Windows 10) neither those mysterious extra symbols nor any placeholders for them appear.
The actual stream of bytes looks something like this: Completeness%3A%20%E2%88%80x%2C%20y%20%E2%88%88%20X%2C%20either%20x%20%E2%89%BC%20y%20or%20y%20%E2%89%BC%5C%5Cu0016%20x
The result of “unquoting” this is: Completeness% [forall]x, y [element] X, either x [leq] y or y [leq]\\u0016 x where the things in square brackets represent single Unicode characters each represented by three UTF-8-encoded octets.
This stuff is all inside a <script type=”text/inject-data”> element, which seems to be some Meteor thing and I don’t know what gets done with it—but presumably it’s being processed by something that interprets backslashed Unicode escapes. \u0016 is an old ASCII control character (yes, the ASCII control characters have Unicode code points assigned to them), the one called SYN. I have absolutely no idea what is the “correct” behaviour for a web browser asked to display a SYN character.
For me right now (Firefox on Windows 10) neither those mysterious extra symbols nor any placeholders for them appear.
The actual stream of bytes looks something like this: Completeness%3A%20%E2%88%80x%2C%20y%20%E2%88%88%20X%2C%20either%20x%20%E2%89%BC%20y%20or%20y%20%E2%89%BC%5C%5Cu0016%20x
The result of “unquoting” this is: Completeness% [forall]x, y [element] X, either x [leq] y or y [leq]\\u0016 x where the things in square brackets represent single Unicode characters each represented by three UTF-8-encoded octets.
This stuff is all inside a <script type=”text/inject-data”> element, which seems to be some Meteor thing and I don’t know what gets done with it—but presumably it’s being processed by something that interprets backslashed Unicode escapes. \u0016 is an old ASCII control character (yes, the ASCII control characters have Unicode code points assigned to them), the one called SYN. I have absolutely no idea what is the “correct” behaviour for a web browser asked to display a SYN character.