Status: We don't have the href, but we do have the id.

src/components/status/status.js

@@ -290,8 +290,8 @@ const Status = {
       }
       if (target.tagName === 'A') {
         if (target.className.match(/mention/)) {
-          const href = target.href
-          const attn = this.status.attentions.find(attn => mentionMatchesUrl(attn, href))
+          const userId = target.dataset.user
+          const attn = this.status.attentions.find(attn => attn.id === userId)
           if (attn) {
             event.stopPropagation()
             event.preventDefault()