Update Shifted keycodes docs (#3575)

docs/keycodes_us_ansi_shifted.md

@@ -1,10 +1,12 @@
 # US ANSI Shifted Symbols
 
-These keycodes correspond to characters that are "shifted" on a standard US ANSI keyboards. They do not have dedicated keycodes but are instead typed by holding down shift and then sending a keycode.
+These keycodes correspond to characters that are "shifted" on a standard US ANSI keyboard. They do not have keycodes of their own but are simply shortcuts for `LSFT(kc)`, and as such send a Left Shift with the unshifted keycode, not the symbol itself.
 
-It's important to remember that all of these keycodes send a left shift - this may cause unintended actions if unaccounted for. The short code is preferred in most situations.
+## Caveats
 
-## US ANSI Shifted Keycodes
+Unfortunately, these keycodes cannot be used in Mod-Taps or Layer-Taps, since any modifiers specified in the keycode are ignored.
+
+## Keycodes
 
 |Key                     |Aliases            |Description        |
 |------------------------|-------------------|-------------------|