Many systems (including Debian, Ubuntu and derivatives like Linux Mint) use
Dash as a noninteractive version of `/bin/sh`, invoked by `make`.
Dash's `echo` command doesn't understand the `-e` option and this generates
spurious output when running `make`. See [a bugreport][0] for one of the
many instances of this bug/feature in action.
[0]: https://bugs.launchpad.net/ubuntu/+source/dash/+bug/72167
The current regular expression is likely to match a lot of stuff, as each
comment that a video has has one of those and it is not clear which one is
the date of the video *upload* itself.