I also used iSubtitle to add soft subtitles to a movie. I had edited the subtitles using Jubler to ensure the layout was exactly what I wanted. I exported the movie with the soft subtitles to iTunes.
When played back in iTunes, some of the longer subtitles, which I set up in Jubler as two lines, and which showed in iSubtitle as two lines, would display as 3 or 4 lines. In the case of 4 lines, the 2nd and 4th lines each only had one word. And as set up in Jubler the line break was after this word.
So:
The quick brown fox jumped over
the lazy dog one day late in summer.
displayed thus:
The quick brown fox jumped
over
the lazy dog one day late in
summer.
So I tried playing the file in my iTunes library not with iTunes but with VLC.
VLC allows you to set the font, size and colour of the subtitles. Not surprisingly the 2 lines of subtitles that displayed as 4 lines when played back in iTunes played back as 2 lines in VLC.
I also tried the same file in Quicktime. It displayed the 2 lines of subtitles as 4 lines. So I can only assume that the issue is with Qucktime.
Robert.