Duplicating Compact Columns plugin?

I don't think so... I didn't look too closely at it, but I thought it just let you merge columns into one...

I want a different value not present in any plugin I've seen so far: The time of the last build, whether it succeeded or failed. I don't want to merge those two columns into one unless I can remove the older of the two.

From what I can gather from the wiki, it seems like the Compact Columns plugin can be indeed configured to display only the absolute build time (see also this screenshot).

I'm still planning to implement it into the extra-columns plug-in, because it's actually already half-way in there anyways.
My plan is to split up the "Build Duration" column and create a separate "Build Start" column,
which can then be configured to show the build start either relative ("2h ago") or absolute (e.g. "2013-12-21 10:00:00").
So I'm merely adding the option to show the absolute time instead of the relative time.

And I think compared to the Compact Columns plugin it would definitely be a more straight forward solution to meet this requirement.

I don't understand how such fundamentally obvious information like last build time is absent from vanilla installation of build server.

Should it be a plugin? C'mon!
Extra Columns or Compact Columns plugins are overkill for that.

No, I would agree if there were no built-in columns like "last duration".
Isn't it too common which for everyone to click (in default view "All") and sort all jobs in the order they were started?

Per-result times can probably be added to the existing core columns as tooltips, similar to what Stack Overflow does on their time widgets. I don't think more columns should be added to core though.

Seriously, we consider use of plugins to be pretty essential for Jenkins – there are (AFAIK early stage, admittedly, but still) plans to move the Freestyle Project type into a plugin.

I actually want to have this new Column replace the two Last Success and Last Failure columns.
I have quite a few jobs that have no failure to report since their creation.
There is a Last Duration column that only applies to one of the values of the two columns - to figure out which your eyes have to scan the line to the beginning to look at the status (or in other words you probably loose the line there and need a few tries to be sure).

We're not removing things, so that's not going to happen. (Or rather extremely unlikely to happen based on my extensive experience working with and on Jenkins)

Fixed in version 1.21 by adding a new configurable column called "Last Build".