Changing emoticons from ticks to crosses and vice-versa could be a fairly significant update, but the way the diffs work with the new square-shaped icons makes it very hard to see this.

Here is an example diff: https://confxhtml.atlassian.com/pages/diffpages.action?originalId=110133252&pageId=110133253

You can see how this appears in different mail clients: http://atlassiansoftware.litmus.com/tests/3850258/versions/1/screenshots

Here's what it looks like in Thunderbird:

I removed the tick and added the cross. Or did I add the tick and the remove the cross? Either way, it is almost impossible to tell from the diff what the change was, as you can't tell whether the background is red or green.