Right now Cognate discards redirects and doesn't show sitelinks to redirect pages. This task is for the second part of fixing this issue. After this both directions of the linking should work. It is illustrated in green in the following sketch:
Just to clarify, we don't want "colow" on Wiki 2 to link to "color" on Wiki 1. We only want "color" on Wiki 2 to link to "color" on Wiki 1 (and vice versa). In other words we just want redirects to be treated as ordinary pages.
If we tried to implement this, we would end up with a confusing situation in case there is more than one redirect to "colow" (I think Lydia actually wrote "colour" on the diagram, but let's stick with "colow" for consistency, I like the sound): So if "color" and "COLOR" both redirect to "colow" on wiki 2, and both "color" and "COLOR" exist on wiki 1, what language links should be shown on "colow"? Should it link to "color" or "COLOR" or both? What if "colow" also exists on wiki1?
Essentially, this feature is incompatible with the notion that there can only be one language link per target wiki.