http://wheelmap.uservoice.com/forums/31554-general/suggestions/1147935-merge-changesets?ref=title is marked as complete, but it's worse than before.
When I submitted the idea to merge simple changesets, the problem have been very, very much trivial changesets.
Now it's changed to the opposite since months: Changes are merged independent of location or contributing user. Most changesets therefore has 1) several hundrets to thousands of changed objects, and 2) a gigantic bounding box. If you ever tried to verify changes like that (as I try to do for my local area with all osm changesets touching this area), you would have noticed, that it's not possible to find out the single change you are probably able to check.
For example see the following changeset: http://www.openstreetmap.org/browse/changeset/9621211
As before, the intention of the changeset concept is not implemented here: it's a big pool of single changes (like before), and it's again much work to find the interesting part.
Where initially we had to go to every single change link (often around 10 changes in short time and area because of one user commiting his knowledge), one had to click through 10 changesets, to verify one object each.
Now I only have to open one changeset - but have to browse through thousands of objects to find the one I want (and am able to) verify.
That's not better then before.
A useful strategy would be to cluster by user or similar area in a time interval of a few hours, i think. If then a changeset contains one change only, that's okay, it's usual that this can happen. But it would approximate the idea of changesets: to keep corresponding edits together while separating different editing actions.
Thanks for your feedback and concrete suggestion. We will discuss how we could make the change sets more meaningful and then update our suggestion here.
Matěj Cepl commented
That is really thorough discussion you have there ... I get changesets like https://www.openstreetmap.org/changeset/42290444 like twice a day.