Seems that deactivating opera://flags/#experimental-start-page isn't available in Opera 31.0.1889.99 anymore.
Is there any other way to solve this (to get rid of those white spaces where names of pages are placed in Speed Dial)?

Would developers please stop mucking about with the Speed Dial settings! I now have some of my icons displaying one way and the remaining the 'new' way, with the latest build 31.0.1889.99. This is rather annoying. At least, give users the option to select one version or another.

Thanks.