You’ve identified an important problem to solve. It’s slightly related to Logging non-numeric output variables.
Guild supports a lot of metadata for runs, but there’s nothing in place to propagate upstream run metadata to downstream, esp for use in compare tables. The upstream flags want to appear in downstream runs but they’re not flags. They represent information about the downstream run. Neither are they simply logged summaries, text or numeric. Guild supports tags, labels, and comments. But these aren’t any of those 
either.
I can suggest some workaround to help you through this but I unfortunately don’t have a solid proposal at this time. This problem must be solved though — so we’ll get there. I’ve bumped this in priority as it’s been lingering too long.
My recommendation, as a way forward in the short term, is to write the values-of-interest to the downstream flags attribute. This will cause them to appear in compare lists.
Here’s an example you can work from.
This is a bit painful, but it should work. Unfortunately I can’t think of a simpler work-around for what you need.