Weebly had a built in blog and commenting setup, but in over 5 years I got no comments. There used to be a forum supported by Teva, but it disappeared all of a sudden. So recently I deleted my unused Forum page.
Now I see that Disqus is supported. Go into the Settings and change Blog from 'Default' to 'Disqus' (Facebook is also a choice). But my existing Blog page didn't seem to have changed. So I created a new blog page to try it out. (But the new Disqus blog page doesn't seem to allow comments!)
What if you want discussion or comments on other pages? Before Disqus was built in, you had to use the 'Embed Code' structure. You can still do that, and it's easy! On the Disqus site, go to your 'Settings' and choose 'Installation'. Don't choose the Weebly icon, but click 'Universal Code' at the bottom. Copy the text the code that gets displayed. Back to your Weebly site and scroll to the bottom of your page where you want the Disqus comments displayed. Grab the 'Embed Code' and drop it on your page. Click the 'Edit HTML' in the box, a pop-up will appear. Then click 'Edit Code' in the pop-up box and paste the Disquss code into that box. It's easy!
Well, the standard Weebly blog is working!