Will do. Thanks for your help.

Dead end - problem still remains. Had to delete font with command line interface.

Will report to see how it goes.

Yes, I didn't lose any data, due to the fact that I kept backups. But this should be fixed - that font is integral to many Win7/8 themes. Ideal solution would be simply to revert to the state it was at 27 - font-family:custom font rather than font-family: Blank.

Is there any other possible solution? I need that font.

I made a custom theme - it's using it. Oh well, will delete font and report results.

EDIT - Worked. CSS still looks like https://imgur.com/Vny3FWd but fonts are visible. Now, of course, problem is that my theme is broken... Thank you for your help.

I assume the settings page is missing all its text too on the new clean install.
I can only assume this is a missing font on your system.
If it were a problem with Opera surely others would have reported it too.
I wish I could help more, but without knowing exactly which font Opera uses for the display of that text, it's hard to troubleshoot further.

Uh, the font that is being used for that text is called Blank.ttf (http://sourceforge.net/adobe/adobe-blank/wiki/Home/).

Will report how it goes.

EDIT : See for yourself. https://imgur.com/wDP3aCo Latest stable build, completely fresh installation etc etc.

Very strange indeed, this is an obviously serious problem that no-one else has reported, which would seem to imply that it's something on your system as a whole that's causing it, not a problem with Opera itself. I assume you've not seen any font problems on any other programs?
Have a look under Settings>Websites>Display>Customise Fonts.
What does that look like?

Sorry for the late reply. For your inspection - https://imgur.com/0IXxHav

Encoding is in UTF-8, fontsize is tiny. I tried to change it to different fonts, but it never worked.

Should add, I did manage to partially alleviate this problem by disabling custom font rendering as in https://imgur.com/Vny3FWd , but it results in opera reverting to default font as seen in https://imgur.com/LfN1xet - it's oversized, and this has to be done for every local page. Websites have no problems displaying custom fonts though - it's just the start page, bookmarks, settings (local pages) that have this blank text problem.

I can only assume no-one else has seen this.
You seem to have quite a few extensions installed, have you tried disabling them all as a test?
It could be one of them causing the issue, and doing this will at least eliminate them.

Disabled them all and tried. It occurs on the web dev builds, and the stable builds, basically anything after 27. The web dev build (I tested on 29) installs itself as a separate standalone version, so no extensions or scripts can mess with the CSS. It happens there as well.