Please keep all discussion not specifically and directly related to the bug to Reddit or the forums. Discussions about why Minecraft was split up this way have been had before and explanations can be found via google pretty easily.
@Pongo Saoiens the mods do have ways to contact Mojang directly but we very rarely contact them directly over a single bug report unless it is a security issue. We typically flag bugs behind the scenes for review which the devs do weekly usually. I will do that here, but beyond that the mods aren't involved in the process.
Please recreate this in a new super flat would and link or attach that. If it can be isolated as much as possible, the devs can do the rest.
@unknown we will take a look (I'm not on a computer I do MC stuff on), but to address your last paragraph - a contrived example is exactly what helps. If it can be reproduced in a brand new, empty superflat world with nothing else but the exact required setup that very much narrows down what could be causing the issue, and as a (non-Minecraft) developer that is always the best info a bug can have. Having it in a real/old world that has tons of stuff in it (Etho's comes to mind) makes it very hard, even if it is known where (roughly) in the world it happens because there is just so many possibilities.
Mojang does most assignments internally, you will not see that field populated until a fix is posted most likely. It does not have to be in a confirmed status to be worked, it just helps.
What would help far more is a known and reproducible cause. The world you provided, per your own description above unfortunately does not count as it has been heavily and repeatedly edited by 3rd party tools, thus Mojang has no clue what has been done. If anyone can identify the error in that world, and reproduce it in a new, untouched map, that would give the developers something to key in on. It is very possible, indeed likely there is more than one issue at hand here affecting different people. There are a ton of people NOT experiencing this issue (I've had no problems resembling this in any of my worlds) and that makes it very difficult to work (or even who to assign it to that would have knowledge of the necessary code areas).
In addition to all that, "lag" is way to general for them to try and do a targeted fix for and thus as @unknown said, they mostly get addressed at the end when developers can spend time on fishing expeditions.
Can I suggest this rather meta discussion be moved to https://www.reddit.com/r/Mojira/ ?
Please do not repeatedly edit your comment, a notification goes out to everyone watching the bug every time you save. There is a preview button if you're concerned about checking the format.
Outdated and broken Intel graphics card drivers, see MC-14051.
Update from http://downloadcenter.intel.com/
This is a technical support issue; this site is for bug reports only. For technical support please use the Mojang Support Center.
@unknown Even when playing single player, the user is essentially running a one player local server (not opened to the network) and a client. This change to a single package was made quite some time ago. Things like tick lag (blocks dropping slow, mobs moving slow) are "server" side while graphics are the client. Some things get more complex than that but that is the basics.
This site is for bug reports only. For feature suggestions or changes please see: Minecraft Suggestions on Reddit. Feel free to post it there, Mojang does look at the list.
This is a duplicate of MC-1823 / an enhancement suggestion. For feature suggestions or changes please see: Minecraft Suggestions on Reddit.
Please use the Crowdin Minecraft Translation Project for all translation change or add requests.
This site is for bug reports only. For feature suggestions or changes please see: Minecraft Suggestions on Reddit.
Unfortunately Mojang can not do anything with or due to external software, you would need to report the bug to Voila.
For feature suggestions or changes please see: Minecraft Suggestions on Reddit.
Are you shift-clicking them into the chest?
You can go to the Minecraft Suggestions reddit and post there, but given the issues this fixes there is almost no way it would be reverted. Given people have already developed item elevators using very close to the previous design there really is no reason.
@unknown Please stop editing your comments repeatedly, the system sends an email to all 72 people watching this bug every time you click save.
As to your last comment, that is not relevant to this or any specific bug and thus needs to move to the Reddit or forums.