I'm a rather thoughtful speaker, so I rarely regret my words, but this is a somewhat separate issue. There are lots of factors that affect how likely someone is to say something they will later regret. The biggest thing that makes people say things they'll regret isn't a language, it's the internet. If you say something you might regret in a letter, it's pretty easy to catch it before sending it. In an email, not so easy. In an IM, you're likely to send the message before you've even read it back.

What this tells me isn't that we need better tools (whether they be software or languages or anything else), it's that sometimes people say stupid things, and we need to be more understanding. A hundred years ago, it may have been reasonable to expect that a long-distance friend would never say anything rude to you, because they'd have time to edit their words. It isn't reasonable to expect that anymore. People haven't changed, but their ability to edit themselves has. Instead of trying to recreate that ability to edit ourselves, we need to evolve our interactions with each other so that these thoughts that we had time to edit before don't play such a big role in our communication.