Welcoming policy
A wiki is only allowed to post welcome messages to users if their account was originally created at the wiki, or the user has at least one non-imported edit there.
Some wikis post welcome messages to the talk page of new users accounts, for example saying welcome and linking to important policy and help pages. Many user accounts at a given wiki were created automatically by the global account system when a logged-in user from another Wikimedia wiki randomly clicked a link to the wiki. Accounts can also be created automatically for users who have never visited the wiki, if the user once edited a page at another wiki and it was later imported with page history. In both cases, the user may have no knowledge of the wiki or its language, and can be confused or worried by unreadable messages. Posts to user talk pages trigger a notification at other wikis and often an e-mail in the language of the wiki.
Welcome messages may both be manually written and use templates. Allowed welcome messages may both be posted by editors and bots. A plus or home icon under "Method" at Special:CentralAuth may show where an account was originally created. As of 2020, imported edits appear to generally not be included in the edit count at Special:CentralAuth.
Wikis are free to make stricter local rules for welcome messages but not to allow more messages.