There's a regexp that SublimeText seems to choke on. It's in JDate, right here:
https://github.com/joomla/joomla-cms/blob/master/libraries/joomla/date/date.php#L281-L285

So there are some lines that look like:

$format = preg_replace('/(^|[^\\\])D/', "\\1" . self::DAY_ABBR, $format);

Inside the [], the first \ (PHP string) escapes the second one and the third is literal. So this give us regexp like /(^|[^\\])D/ in which the first one again (regexp) escapes the second one.

I think I know why SublimeText acts funny here but it doesn't matter much. I wonder if (for the benefit of us ST users) the string could be changed to:

$format = preg_replace('/(^|[^\\\\])D/', "\\1" . self::DAY_ABBR, $format);

I don't think it makes any difference as far as they way the code works. Am I missing something?