So my RTL theme behaves like this with 1.8.3 :
How can I make it correct like all previous version (small on the right of the text with two small up and down arrows) ?
Not sure which theme you're using (looks like a mix of Snow and SnowFlat) but I guess it hasn't been updated for 1.8.
You could try adding some of the CSS from the SnowFlat theme. You'll need the ".qa-c-list-item" styles as highlighted here. And you'll need to update this section here with the vote-buttons-2 image.
Otherwise, contact the theme author and ask them to update the theme.
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April 20, 2021: Q2A 1.8.6 released!