Ignaz Forster

The affected chests were not created with any 1.7.x version, but in way older versions. I don't think anybody researched the exact version where the chest behavior was changed, but https://bugs.mojang.com/browse/MC-70813?focusedCommentId=202853&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-202853 explains the technical problem (i.e. the way chests are saved seems to have been changed somewhen, and since version 1.8 Minecraft is not able to understand the old format any more, though it's still present in the maps for old chests).

Thus marking this problems as fixed is definitely not correct - but I guess most people won't care about a fix any more because they either lost their data already or converted the map in the meantime (e.g. by using one of the attached scripts).

Eventually. There's one difference between those bugs, though: MC-6726 had that error when migrating to MC 1.4.7. At least our world had no problems during that update, but is now breaking with 1.8. This may indicate that it's a different error. In any case a defect example world is probably needed first.

I don't think this ticket and MC-6726 are duplicates of MC-2548. MC-2548 tells about complete chunk resets, while MC-6726 and this ticket only tell about lost chests (and some strange water behaviour), while the remainder of the world (e.g. the houses the chests were in) stays intact.

Confirming the chest problem: Many (probably older) chests just disappeared after the upgrade to 1.8. We've also rolled back and upgraded sequentially, but the chests disappeared again with 1.8.
Unfortunately the world is too large to upload anywhere - Peter, did you manage to upload yours somewhere?