Incorrect identification of scope of a macro definition
Consider the following example
Observe that the final three characters -- )}} -- aren't colored green even though they clearly belong to the scope of the argument of the \sorted macro.
The remedy would be not to look for the very first instance ...
@ ("at") isn't recognized as a valid character in a command name
Many hundreds (thousands?) of LaTeX2 commands employ the @ character in their names -- usually after one issues an explicit or implicit \makeatletter directive. Consider the following example (taken from an old answer of mine):
Very difficult to distinguish comments from ordinary text.
Hello World. % A comment.
The shade of gray that's used to highlight what's a comment is quite dark, making it anything but straightforward to identify comments visually. Please reinstate the old scheme, which used a much lighter shade of gray to denote comments.
LaTeX3-semantics for valid macro names aren't recognized.
With LaTeX3, the characters _ (underscore) and : (colon) may be (in fact, must be) used in various macro names. Take the following code snippet:
\seq_set_eq:NN \l__ralph_seq \l__alph_seq
\seq_set_eq:NN \l__rAlph_seq \l__Alph_seq
\seq_set_eq:NN \l__ralphAlph_seq \l__alphAlph_seq