As a consequence of merging #5221 it is more likely to have multiple
overlapping selection divs inside the text layer. Because each individual
element gets the selection style applied, the 30%opacity stacks, making a
60% bar visible where the overlap happens.
As proposed by @rocallahan, this can be fixed by making the selection
style solid and setting opacity for the overall layer.
I assume also that this should make the work for the renderer easier, but
was unable to bench it.