Created an attachment (id=8250) [details]
Partial screenshot, showing the problem

This spacing is slightly off - see, in the attached image, many of the tabs,
but especially the one called 'Abre' and especially the separator following it.

I am using the default theme in the screenshot. I think that with some other
themes the problem appears worse.

Thanks for your time.

First of all the reason for the rule: I noticed that the label text was
squashed against the icon if the button contained an icon, so I had added the
(rather heavy handed) rule:

#QuickFolders-FoldersBox toolbarbutton label {
  padding-left: 0.2em;
}

Ideally I would only want this to be visible if there is a visible icon, which
is actually harder to achieve. I will try and add it to the icon instead and
hope that it isn't shown when the image is empty.

Created an attachment (id=8251) [details]
4.6.1 prerelease 46

The problem of the extra space was persistent for all styles (not just
pushbutton mode) without icons. Among other things I had to remove the "icon"
class and did a bunch of restyling for these buttons - hopefully this version
fixes it sufficiently. Note that the distance of the icon (if shown) and the
label is proportional to the button's font size (0.4em).