Merge questions from different sites

Question

A user has posted an identical question on both SO and DSP:

SO: remove the holes in an image by average values of surrounding pixels
DSP: Interpolation of a gray scale image in matlab

From reading through posts on here I see that this is discouraged, so I have commented on each question with a link to the other, and flagged for attention.

The thing is, while (in my opinion) the question is a better fit for DSP, I can see that it is a borderline case, and it has received more answers (and up-votes) on SO.

Is there sometimes justification for asking these overlapping questions on a specialist beta site, as well as the large volume SO, to ensure a quick response/maximum exposure? Should these questions be merged, and if so on which site?

Answer 1

The solution is to migrate the question to the more appropriate site (in this case it's a moderator only action) and then get the moderators to merge the questions on the target site.

If there are no (good) answers on the incorrect site then just close the question as off topic.

Answer 2

In this case, one question is more specific than the other, as the question on Signal Processing asks how to do it with Matlab, while the question on Stack Overflow doesn't ask how to do it with Matlab.

I think the question could be asked in two different sites, if the question is made specific for the site where the question is being asked. For example, if somebody asks the exact same question on Drupal Answers, and Stack Overflow, where Drupal questions are on-topic, that would not be acceptable.