During a discussion on EL&U about a link to an ELL question that someone added in a comment, Laurel had an idea to show links on both sites if someone linked a related question on the other site:
As long as these comments are done politely (as this one was), I think it's helpful to link to relevant questions on other sites. In fact, I think it should be taken a step further, with "association banners" like some questions on SO have to Ru.SO questions. (Due to the language difference, these banners are only visible to people with certain browser settings. I'm not sure if there are any plans to bring this feature to the rest of the network unfortunately.) – Laurel Mar 30 at 14:52
It does seem like a good idea, and we found an existing feature request on Meta that had been declined that we are trying to resurrect: Display other SE site links in the linked questions sidebar. Part of the reason the request was declined according to Jon Ericson's answer is that it is more work than the value it seems to add:
I suggested this feature to the dev team. It turns out the linkback feature makes it difficult to implement and expensive to put in operation. (snip) So while we think it's an interesting feature, it's not one we will be investing in anytime soon.
aparente001 has posted on the EL&U meta asking for community support to get this feature reviewed again (since it has been several years since it was declined). I'm asking for the ELL community's help as well. It's not unusual that there is a question on EL&U that discusses the same topic as a question on ELL but from a different perspective. It would be nice if the question on EL&U linked back to the ELL question so that someone who came across the EL&U question, but was looking for an explanation from a learner's perspective could more easily find the ELL question.
If you think that feature might be a good idea, please visit the Display other SE site links in the linked questions sidebar and support the favorable answer (or add your own answer proposing what you think might be a good solution).