4.8.10 on jolla, merge works fine it seems (compared two similar files, one with extra line, after merge it got added to the other and asked if to save changes on exit)
Diff viewer Bidirectional merge (F5 merge left-to-right, F15 - merge right-to-left) (#2863)
mcdiffviewer can merge only from right panel to left panel file. It will be nice, if -- similar to edit and edit other -- mcdiffviewer can merge hunks into the opposite directions too. This patch add this feature to mcdiffviewer. With F15 mcdiffviewer merge left panel to right panel direction.