I have long been looking for a plugin that would enhance WordPress' comment system with some AJAX features, specifically, it should:

• a) enable AJAXified comment posting without the need to reload the entire page after a comment had been submitted.
• b) enable AJAXified comment paging so that people who read larger amounts of comments do not need to reload the complete page.

There have been a number of solutions for both a) and b) but none that combined everything into a single plugin and some of the AJAX commenting plugins are outdated and incompatible with recent releases of WordPress and many modern themes.

The mother of all AJAX comment plugins

That pretty much sums it up. WP-Comment-master is the most comprehensive WordPress plugin to AJAXify the comment system. It has all the features, installs quickly and does not need any changes to your theme. Basically, it does 2 things:

• enables AJAX paging for long comment threads. Visitors can load a new page of comments without reloading the entire page. Not only does this accelerate the process of paging through many comments, it will also reduce the load on your server.
• enables AJAX comment posting. After submitting, the new comment will instantly appear in the comment thread, again without reloading the page.

The plugin does not need any changes to be made to your current theme (assuming, you're using one of the modern WordPress themes and did not heavily modify the comment templates). It requires JavaScript (of course, like all AJAX features do), but for users who visit with JavaScript disabled, it also provides a fallback mode and these users will see the default (non AJAX) version of the comment paging and posting - just like it works without this plugin installed. It's also lightweight and has little, if any, impact on the performance and because users can page through comments without reloading the whole page, the overall server load should benefit from this plugin.

SEO considerations

One often heard argument about AJAX is that it can have bad side effects on the indexing of your page(s). There is some truth in this argument and one must know what AJAX really means to understand. All AJAX techniques work by modifying pages that are already fully loaded and visible in the browser. By sending asynchronous requests and using the replies from the server to manipulate the HTML document via its DOM, AJAX features can change the content of a page without completely reloading it. Another important thing is that all AJAX techniques are closely bound to the availability of JavaScript. No JavaScript - no AJAX.

Said that, it should be obvious that AJAX can only work in a browser with JavaScript enabled. Search engine crawlers cannot use these features and will continue to index pages using only conventional HTTP requests. The good news is that this plugin is not going to affect the crawlability of your site in a negative way. Just like when a visitor with disabled JavaScript visits your site, the plugin will present a standard comment page to the search engine so that all comments can be indexed like before.

Conclusion

Put simply, this is one of the best plugins ever made for our favorite blogging software. It really enhances the commenting system for your visitors and can help to reduce the load on your server(s) when you have many large comment threads and want to use paged comments.