Double-click selection in the expression editor isn't context-aware. In almost every other application, double-clicking selects a token based on its surrounding context — a single field/identifier when clicking on a field, or the word boundary within a string literal when clicking inside quotes. The expression editor doesn't respect these boundaries, so its double-click behaviour is inconsistent with the standard expression-editor behaviour users expect.
Expected: Double-click selects the relevant token based on context (e.g. an individual field reference, or a word within a string literal).
Actual: Double-click selection ignores context and does not match the token/word-boundary behaviour found in virtually all other expression editors and text inputs.