By default, WordPress allows certain HTML tags such as <a>, <strong>, and etc within the comment box.
To make them work, your readers need basic knowledge of the html tag. For example they need to know <strong> tag is for bolding text and etc.
So if your site comprises of mostly not tech savvy readers, then you can make use of the Basic Comment Quicktags plugin.
With Basic Comment Quicktags plugin, you will get quicktag buttons of html tags shown on the comment box for your readers to quickly or easily format their comments.
To get this feature, all you got to do is to install the Basic Comment Quicktags plugin in your WordPress, go to the WordPress Dashboard > Settings > Discussion and tick the checkbox of Activate Quicktags for comments to enable this function.