The issue of editing root nodes is considered a feature, and not a bug. I don't totally agree with the policy, but I do understand the reasons for it. Changing a top-level node can cause havoc (or at least some extreme out-of-context replies). Hence, the mighty "Preview" tag. Some top-level nodes *can* be edited (e.g. snippets) but in general, you just have to be really careful. Extreme errors can be changed by making a petition to the gods. For minor ones, replying to yourself is sometimes the best way to go.

Don't worry about making a post you later regretted or really, really wanted to edit - we've all done the same. Consider it a rite of passage. :)