The standard policy for blogs and online forums is for everyone to be free to add comments unless they repeatedly violate rules against swearing or personal abuse. In the past I have taken this approach on my personal blog and Facebook profile and so only blocked a handful of people over many years. This policy ensures that all comments, even those judged negatively by the original author, can be found somewhere in the resulting thread. But it has some major downsides, and I now wonder if it was a mistake.

People who write outrageous things and get banned never last long enough to do much harm. The real damage is done by frequent commenters who are uninformed, thoughtless, long-winded, mean-spirited or uncharitable. I have inadvertently wasted a lot of time over the years reading and responding to the resulting comments. While I could ignore them, that allows incorrect claims or poor character to go unchallenged. Even if I knew I were wasting my time doing this, obnoxious comments preoccupy me and lower my productivity whether directed at me or others. Many readers start scanning comment threads and I imagine they can find the experience similarly draining.

The worst case scenario is the ‘comment thread death spiral’. The best comments typically come from those whose time is most valuable: busy professionals who actively study or work in a given field. But comments threads are naturally dominated by those who spend much of their life on the internet commenting on blogs and often bring no particular expertise. Each foolish comment lowers the signal-to-noise ratio and reduces the attention good comments receive. This wastes everyone’s time. But it is particularly particularly annoying for ‘busy but informed’ commenters who barely have time to read the original post, let alone wade through lengthy comment threads. They realise their remarks will be crowded out by others, or they will have to wrangle with uninformed responses, and rationally opt out. As a result, bad comments disproportionately drive away the best ones. The average quality of comments falls and the cycle repeats. This partly explains the negative correlation between the quantity and quality of comments between blogs.

Despite the damage they do, most authors refuse to warn or block those who leave lousy comments because they do not violate social norms, and in most cases mean no harm. It is impossible to set up clear rules to specify which comments are helpful and which are not. Instead, the author must exercise a lot of responsibility and discretion, which they do not want to do because it is time-consuming and opens them up to conflict and criticism.

A nice alternative is up- and down-voting, which has worked well on Reddit and Less Wrong. This allows (anonymous) readers to notify everyone else about whether something is worth reading before they bear the cost of doing so. Modules for this are tricky to set up, and rely on a large, active and intelligent audience of voters. But they are invaluable and ought to be the default. A simpler option would be ‘highlighted comments’, which would let the author pin the best comments at the top of the page.

Where those options are unavailable, should we worry about authors choosing which comments, or commenters, remain on their websites? I think not. Most writers want to offer readers a good experience in order to attract more of them. When choosing commenters they will bear this in mind, just as they do when choosing the content of original posts. If you find their writing worthwhile out of the millions of blogs and books available, you can probably also trust them curate comments effectively if given the chance. Where they don’t, you can seek responses elsewhere or vote with your feet and read someone else. Personally, I feel that the benefit of not having my time wasted vastly outweighs the risk that I will be prevented from reading good responses, or have my own removed.

We don’t let strangers without interesting things to say interrupt and talk over conversations with friends and colleagues. We invite the people we want to our seminars, parties, and so on. Despite some drawbacks this model works pretty well, and it should be acceptable online more than it is today.

Update: a similar point made by someone familiar.