There indeed may be some clipping seen, in EE+ALM mode, in certain conditions (camera altitude, haze settings), however the worst I could get is this:
This is under Linux and strangely the same viewer version but in its Windows flavour and ran under Wine seems less affected (barely visible clipping); so the importance (and visibility) of that glitch may depend on your graphics driver !
I cannot reproduce the glitch in LL's viewer, but the latter is "cheating" since it makes the Sun vanish into the haze at the horizon, meaning the Sun disc is never seen intersecting the horizon (and if you reduce the haze density to 0, the Sun vanishes entirely, which is of course a (much worst) bug !)...
I therefore infer that there is a slight difference in the shaders (probably coming from a fix for the haze that I backported from another viewer at some point). This is likely some parallax effect (Sun object is in front of the horizon ?). If anyone competent enough in 3D rendering and shader programming can detect the bogus code, I'm all ears !