You can only edit them for a short amount of time. The mods changed this because people would ask a question, then change their question around and peoples answer would no longer correspond to the matters at hand. It works, and doesn't at the same time, but in essence does save some confusion.
I think you have about 20 minutes to edit your post after you click Submit, then you can't edit any more. Just use the Preview button and proofread a couple times before submitting your post or response and you should be fine.
It indeed is only available for a very limited time after posting. If you need something repaired or feel something should be removed/locked then please contact a mod.
The only time I am bothered by this change is on my reviews I like to update them with durability information. I've changed to where I just add a new post now but it would be nice to be able to complete the actual "review" as well.