Nether Brick slabs occupy already existing Damage Value ID

FYI: 44:7 and 43:7 are now the seamless slabs.

I don't care what the new ID is. It's still breaking millions of worlds and builds. It might as well be nuclear meteor showers; it's just as destructive.

Reopening for Mojang to decide.

It's not quite on the level as destruction you suggest. You can use MCEdit to update all the blocks from 44:6 to 44:7 and 43:6 to 43:7.

When implementing bugs as part of a build, it should be understood that the bug can be fixed at any given moment. Maybe it looks aesthetically ugly, but that can be fixed with MCEdit. If you say 'I don't care...', why should Mojang care about you? This doesn't break any mechanisms like redstone at all.

For a short time these blocks were available in survival by exploiting a block transmutation bug. Mojang quickly fixed this bug, but did not turn the blocks into double half slabs as they easily could have.

I am sure that Mojang were aware of the block's existence through LPers, for example Etho (who Dinnerbone watches) used these in a recent episode: http://www.youtube.com/watch?feature=player_detailpage&v=Io668pODsEA#t=271s

And if Mojang was aware of this block and its aesthetic uses (very likely) and they did not add it into the game officially, that would suggest they do not want to include it in the game or that they are still thinking about adding them.
This ticket is very borderline feature request, as it is basically suggesting:
1. Add the smooth stone slab (back?) into the game
2. Change the ID of Nether Brick slabs to metadata 7, hence 'breaking' any snapshot builds utilizing this block. Very hypocritical, as the main argument here was that the nether brick slabs 'broke' builds that use smooth stone slabs.

There's quite a difference between a recent snapshot (without which this can't even be discussed) and the many updates of it existing beforehand. This isn't hypocritical in the least, on the contrary it needs to be brought up and come to a final conclusion at quickly as possible for that reason.

I don't see any reason in why Mojang didn't add the new slabs as 43/44:7 instead.
Mojang has never done this before (replace block IDs and break existing builds) - I don't understand why they did this time.

When flammable wooden slabs were added, the pre-12w17a slabs were still kept as they were and the new slabs were instead given a different ID.
Why not the same with Netherbrick Half Slabs?

This is something I would like to see changed/fixed. Or having the smooth stone slabs created into an official (but uncraftable) block for the next releases as 43:7 and 44:7 so that such additions will no longer affect it.

This change also affected many other things than just worlds, but plugins like dynmap which a lot of servers use. While dynmap is upgradeable, as well as worlds, it really is a lot of effort for the Minecraft community to do so, when Mojang barely has to do anything to change this.

I made an account just to tell you how much this effected my server. This change was not only unnecessary, but was easily avoidable by making the Nether Brick ID 43:7 and 44:7 respectively. This also broke a lot of the map rendering software that I use for my server as well. Many players have dedicated a lot of their time to create beautiful projects and were horrified when they logged on and found that their creations are now all Nether Brick.

Can at least someone from Mojang explain the reason behind the change? Ignoring this issue won't help us at all; and if they don't revert the ID value, that's fine. At least tell us why you did it, though.

To say this is frustrating is an understatement.

Because double netherbrick half slabs are officially part of the game in a full release it is too late to simply change the data value without breaking people's legit builds. Pre 1.4.6 maps can only be fixed by mapmakers by changing 43:6 and 44:6 blocks to 43:7 and 44:7 blocks.

However, unless Mojang address this issue and guarantee that 43:7 and 44:7 will not be overwritten in a future update, this issue will most likely happen again.

It is a shame that this issue which had an incredibly simple fix, and has disfigured scores of maps, has been completely ignored by Mojang despite being on the bug tracker.

Metadata is precious. There are only 4 bits per block, and thus 16 possible values. For slabs, the most significant bit is used for orientation (1 == upside-down, occupies the top half of the block instead of the bottom half). That only leaves 8 possible varieties/textures, of which they've now used 7, including the unburnable "wooden" slab that was kept as a concession to existing maps.

What people are suggesting is that they reserve the last available value for a block they never intended to exist, and you've never been able to get legitimately? It's one thing to expect them to never break legitimately built maps with an update, and another entirely for them to never break unintended things created through unsupported methods. You had to do something outside the norm to create it in the first place, so you should expect to do something equally outside the norm for it to survive an update. The game as intended should not be harmed or limited by the developers bending over backwards to support things they never intended.

I agree with your point that as there is a limited amount of metadata, and that not fully supported blocks should be first to be replaced when the limit is reached.

However, the limit still has two more metadata spaces before seamless blocks would have to be removed. The developers would not have to bend over backwards at all, and the game would be harmed in absolutely no way if netherbrick half slabs had been made at metadata 7 instead of 6.

The Seamless stone slabs are attractive, a lot of people like to use them. There's no reason why they couldn't make them obtainable. 2 Stone Slabs crafted side by side (shaped recipe) turns into 2 seamless stone slabs. 2 Seamless Stone Slabs crafted side by side turns them back into regular Stone Slabs.

Mods have been created that allow you to obtain them, they're included in Feed the Beast and other mod packs, a large number of people are putting these into their maps and they should be supported at this point.

And now, in the new snapshot, quartz slabs have been added that use 43:7. When will the War on Concrete end?

"Affects Version/s" needs to be updated.