Flasheek

All I can see is that you are trying to power a dirt 2 blocks below the door itself. I see nothing wrong here 🙂

Confirmed in 13w02a-b. Unable to make a map-pixel-art :C

I don't think the immediate explosion caused by derailing is a good idea at all. You can accidentally slightly push it off the rails and die for no reason.

Minecarts actually have the minimal speed for derail explosion, but this speed is so little it makes no sence. But explosion, caused by going off the rails on high enough speed sounds like a nice idea. Useless, but nice 🙂

Yup, intended and, actually, very useful. Often you need to power lots of com.blocks because they execute only one command, and placing them in pattern Block-Repeater-Block-Repeater allows you to create pretty compact contraptions

Or I'll just attach a couple of images

Confirmed in 13w01a-b, this time caused by new Redstone Blocks. Description and a couple of ways to reproduce here: MC-6005

Alllrighty then

Tails, wait. I don't think so. I was updating this page, describing why it is not a duplicate and directly related to the new redstone blocks, when you marked it as dupe :c

OK I got it. I hope you don't mind me adding this way of reproduction to MC-6005 Description

Wait.. how exactly you did this? I can't reproduce it your way

You may want to add your second image as a comment to the MC-6005. This is a really nice way to reproduce this bug

since sprinting was implemented

This is intended

As of 13w01a you can duplicate rails even easier. Also works with trap doors.