A difference about the bioinformatics comment Larry made on the question here was partially answered in a comment there, and again be the moderator in an answer - that was about migrating, which isn't possible for older questions.
Generally speaking sites like to keep their popular Q&A's and the interest they generate.
OTOH, if you spot a good question (regardless of upvotes) that is old and has no answers (or any answers that have been poorly received) it is polite and helpful to write a comment on the question on the other site informing the OP that our new site would welcome their question here (especially if you are willing to answer it here). It's better to get credit for an original answer here than to take (or wiki away) credit for a question from another site.
The OP gets credit for their question and hopefully a better answer, while some of us gets credit for answering. Be certain to remind them to use the share link and edit their question on the other site with a link to their question here (and vice versa).
This is helpful for old questions without suitable answers and questions that were closed as off-topic on the other site (as long as they are on-topic here). Don't do it to new questions, as such actions won't be appreciated (poaching).