Some people feel that such phrases add no information and should be stripped in favour of brevity. I disagree. These phrases act similarly to prosody (inflectio

Some people feel that such phrases add no information and should be stripped in favour of brevity. I disagree. These phrases act similarly to prosody (inflection, tone of voice), adding some often hard-to-define context as to the nature of what is being said. This particular phrase indicates that what comes next is not part of the main thrust of the argument but a side observation in support of it. It prepares the reader or listener to receive it in that spirit rather than have to figure its status out for themselves. Used superfluously or incorrectly it can be pompous and empty, but used well it can genuinely improve comprehensibility, even if a word processor's grammar checker might choose to put a squiggly line under it.