Compare any two revisions: Improve the distinction of From/To columns

[birgire]

This is a continuation from ticket #43532.

We have a From/To when the "Compare any two revisions" is checked, but it might not be obvious what column is From and what column is To.

Here are relevant comments from the #43532 ticket:

@adamsilverstein suggests using e.g. "added" and "removed" (see here https://core.trac.wordpress.org/ticket/43532#comment:5 )

@kjellr mentioned that this was discussed in design chat
https://core.trac.wordpress.org/ticket/43532#comment:19

The Design team discussed this briefly in our triage today:
​https://wordpress.slack.com/archives/C02S78ZAL/p1564417984166900
(A WordPress.org slack account is required to view that link)
Both of these updates seem like solid improvements, and the screenshots look good. We're >going to remove ux-feedback for now.
Thanks, all!

I'm adding the screenshots here below:

[adamsilverstein]

Hi @birgire thanks for opening this ticket. It is clear the display needs improvement here to make it clearer whet the user is seeing.

An important point (that confuses many people) is that the two columns always represent what was removed in the left hand column and what was added in the right hand column. (except in the filter enabled single column view where additions and deletions are displayed in a single column).

Changing the placement of From/To to above the columns will further confuse things. Maybe we can instead add column headers that say "Added" and "Removed" to make it clear these aren't before/after columns.

[birgire]

Thanks for clarification and the screenshots @adamsilverstein

Related #25473

[SergeyBiryukov]

Related: #48574