In the RevisionSlider popup, there is no space before the edit summary of each revision (see screenshot).
Once https://gerrit.wikimedia.org/r/#/c/301338/ got merged this should not be an issue any more. Previously an i18n must have included a trailing space if there should be a space between a colon and the summary.
I suggest we wait until new version gets deployed on dewiki and then close the ticket if the issue is gone
(And, might I add, it's pretty hard to debug it using the dev tools, with the popup disappearing on mouse out. Is there a trick to overcome this annoyance?)
What you'd need to do that is indeed a trick. E.g. you could change the hideTooltip function in modules/ext.RevisionSlider.RevisionListView.js so that it does not hide the tipsy tooltip (ie. remove temporarily $rev.tipsy( 'hide' );