'MergedInto' rows in Links table

In the mysql database for my 2.0.11 install, I’ve got 439 rows in the
Links table where Type is ‘MergedInto’. For all but 8 rows, Target is the
same as Base and LocalTarget is the same as LocalBase. Since merging
works correctly, I assume these rows are completely ignored. So why are
they there in the first place? It’s also odd that 8 rows somehow were set
correctly, but all the rest weren’t…