The feature is part of Auto-tagger.
- Orphans are articles with no mainspace incoming links to themselves or their redirects.
- Orphan tagging is optimised for en and ru wikis.
- In ru.wiki adds linkless to isolated articles if article has 0 incoming links.
- It's strongly recommended to enable "Restrict orphan tagging to linkless pages" on the options menu. This reflects current consensus in en.wiki and it's always the case for other wikis.
- This restriction is enabled by default.
- Auto-tagger won't tags redirects, soft redirects, dabs, set index articles and it will untag them if they are tagged already.
- Auto-tagger excludes from point counting redirects and non-mainspace pages.
- Auto-tagger will tag as an orphan an article that has 0 incoming links to itself or its redirects that there are not redirects.
- Incoming links from disambiguation pages aren't excluded from page counting. This results in pages with many links from dab pages to be untagged.
- This doesn't seem to be a big issue though since the definition is quite loose at the moment.