Agreed with @codebrainz it's not very clear, but I guess I got it:

When *filetypes.php* has an empty `comment_single`, it uses HTML comments (`<!-- -->`) instead of multi-line PHP comments (`/* */`) for some reason. To test:

1. Open Geany with a stock configuration (`geany -c /tmp/temp-config`) 2. Create a new PHP file from template 3. Insert a non-empty line in the PHP section (e.g. `echo "hello!";` on line 24) 1. Try and comment line 24 with <kbd>Ctrl+E</kbd>: it inserts `//~ ` at the start of the line. Good! Try and the same on line 31: it inserts `<!-- -->`. Good again! Toggle both back to not commented. 4. Open *filetypes.php* (*Tools → Configuration files → Filetype configuration files → Scripting languages → filetypes.php*) 5. Change the value of `comment_single` to make it empty. Save it. 6. Try commenting line 24: it inserts `<!-- -->` 😞