Does this issue occur when all extensions are disabled?: Yes

Double-clicking non-letter characters selects the neighboring space instead of the character itself. See attached screencast.

Sample text:

// a b c 1 2 3 ~ ! @ # $ % ^ & * ( ) _ + \ /
// aa AA // ← double-click the first character of these pairs

Steps to Reproduce:

1. Paste the sample lines above.
2. Double-click on a symbol like @, #, !, \, or /.
3. Also try the first / in //.

Expected:
The clicked character (or token, e.g. //) is selected.

Actual:
The adjacent space is selected; the symbol itself is not. For //, double-clicking the first / selects the space next to it, while double-clicking the second / selects // as expected.

Please see the screencast to better understand what is happening.