How off-line is Joomla!’s off-line mode?

Joomla!’s temporary off-line mode is a very handy option to temporarily take your site down while performing maintenance —e.g. updating the Joomla! core or an extension— and is even suggested by the official documentation for the unfortunate time that your site has been compromised. However, is this really off-line, or are there any pitfalls you […]