Given wikitext on consecutive lines, such as this:
O what a goo se I am
the result will be shown to the reader as a single line, with the stray break being turned into a space: O what a goo se I am
In the visual diff, it looks like these are being shown as separate lines, which feels a little strange:
It is, however, a dramatic improvement over the wikitext diff for the same change:
Since line breaks are shown as ↵ while editing in VE, it probably would make sense to use <del>↵</del><ins> </ins> to show such a diff.
This behaviour is caused by the CSS fix to T170114, which preserves whitespace in removed/inserted content, so we can see removed/inserted spaces properly. There's a slight inconsistency in this fix: whitespace is collapsed if content is unchanged, and preserved if content is changed.
I agree that preserving line breaks is confusing, since they're not preserved in the visual editor view, and that it would be better to replace them with ↵.
I think we should also use ↵ within the unchanged content, because otherwise the mixture of read and edit views could get confusing. (I suspect that in most cases, the inconsistency with collapsing/not collapsing spaces won't really be noticeable.) Also, the diff view already has some similarities to the edit view, e.g. showing comments.
Change 453463 had a related patch set uploaded (by Tchanders; owner: Tchanders):
[VisualEditor/VisualEditor@master] Show whitespace HTML chars in converter preview mode
Change 453463 merged by jenkins-bot:
[VisualEditor/VisualEditor@master] Show whitespace HTML chars in converter preview mode
Change 454309 had a related patch set uploaded (by Jforrester; owner: Jforrester):
[mediawiki/extensions/VisualEditor@master] Update VE core submodule to master (a8116266a)
Change 454309 merged by jenkins-bot:
[mediawiki/extensions/VisualEditor@master] Update VE core submodule to master (a8116266a)