The LangLinkHandler is the class that puts site links from wikidata into the sidebar as language links. This should only include links in the wiki's own site group (or in a configurable set of site groups), so that in wikipedia's side bar, there are only links to wikipedias in other languages, not links to sister projects that have pages about the same item.
This is currently not the case, the sidebar will contain links from all site groups.
Version: unspecified
Severity: blocker