I wish to move a partition that is part of software raid0. I've backuped, unmounted and stopped raid0, can it simply be moved with gparted like ordinary partitions? (gparted wrongly sees it as almost empty)
thanks.

No. Create a 1:1 copy of it elsewhere, then move the partition and put back the copy. The problem with RAID 0 is that it stores data randomly on all partitions. Loose one partition and all data is lost. RAID 0 may be possible, but is not recommended because of that. My advise would be to upgrade to a RAID 1 or if possible RAID 5. RAID 1 is basically a simple copy of one disk on the other, RAID 5 gives you some data integrity protection (at the expense of a 3rd disk, but those aren't too expensive these days). I use a RAID 5 myself.

but why can't it be moved, sector-by-sector?

edit: solved, by using sector-by-sector move.