We should require user signatures to contain at least one link to their user page, talk page or contributions.
Various tools don't work correctly when such a link is missing. For example, Echo notifications are not sent, DiscussionTools will not allow replying to these comments, en.wp's [[https://en.wikipedia.org/wiki/User:SineBot|SineBot]] treats these comments as unsigned.
Such requirement has been present for a long time in many wikis' policies, but it's not enforced my software. Hopefully this is not a controversial requirement.
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Example wiki policies that require this:
* https://en.wikipedia.org/wiki/Wikipedia:Signatures#Links "Signatures must include at least one direct internal link to your user page, user talk page, or contributions page"
* https://de.wikipedia.org/wiki/Hilfe:Signatur "Eine korrekte Unterschrift enthält einen Link zur Benutzer-, Benutzerdiskussionsseite oder Beitragsliste" = "A correct signature contains a link to the user, user discussion page or list of entries"
* https://ru.wikipedia.org/wiki/Википедия:Подписывайтесь_на_страницах_обсуждения#Собственная_вики-разметка "В этом случае в поле «Новая подпись» обязательна хотя бы одна ссылка на свою страницу участника или обсуждение участника." = "In this case, at least one link to your participant’s page or discussion of the participant is required in the “New Signature” field."
* https://es.wikipedia.org/wiki/Wikipedia:Firma_de_usuario#Consideraciones_de_carácter_obligatorio "La firma debe tener al menos un enlace a la discusión de usuario." = "The signature must have at least one link to the user discussion."
* https://it.wikipedia.org/wiki/Wikipedia:Personalizzare_la_firma "La firma deve sempre contenere un wikilink alla pagina utente o alla propria pagina di discussione (auspicabilmente a entrambe)." = "The signature must always contain a wikilink on the user page or on its own discussion page (hopefully both)."
* https://zh.wikipedia.org/wiki/Wikipedia:签名 "若用户对默认签名进行修改,修改后的签名中必须至少包含该用户的用户页、讨论页或贡献页其中一项的链接。" = "If the user modifies the default signature, the modified signature must include at least one of the user's user page , discussion page, or contribution page."
* https://ja.wikipedia.org/wiki/Wikipedia:署名 "ただし、このチェックを入れた場合でも利用者ページか会話ページへのリンクをどちらか片方残しておくようにしましょう。" = "However, even if you check this, keep either the user page or the link to the conversation page."
(Although I also found a few wikis that don't require it:)
* https://fr.wikipedia.org/wiki/Aide:Signature Only strongly advises that notifications won't work without it
* https://pl.wikipedia.org/wiki/Pomoc:Podpis_wikipedysty Only advises that the signature should include your login