Links containing markdown-like text passed incorrectly

[lheckemann]

{
 […]
 "content": {
    "body": "<https://twitter.com/_julijane_/status/1191323349609254912>",
    "format": "org.matrix.custom.html",
    "formatted_body": "<a href=\"https://twitter.com/<em>julijane</em>/status/1191323349609254912\">https://twitter.com/<em>julijane</em>/status/1191323349609254912</a>",
    "msgtype": "m.text"
  }
  […]
}

I'm not sure to what extent this is a slack bridge problem and to what extent it's a Riot problem (riot has its own problems when you try to send this URL in a chat: element-hq/element-web#4674), but I don't think this message should be getting those <em> tags.