I think they're doing lot of changes in production since every now and then I will run into a glitch. About a week ago I couldn't reply to anything and it seems others were having that issue too, but it was fixed in a few hours. But overall it works fine other than those random incidents.
If you want to use an unusable site, check Facebook.

Holy crap it's so glitchy and it keeps getting worse every time they do an update. I barely go on there anymore because of that. The feed is crap now anyway. Lots of garbage instead of stuff friends post.