Answer:

Confluence does not support the use of Gravatar.

提案:

• There is an open feature request that you can vote and watch:  CONF-19636 - Getting issue details... STATUS

• Workaround is to use the following plugin instead: Gravatar for Confluence

  This plugin is unsupported. please use it at your own risk as Atlassian can not support it.

• More ideas and workaround from our Community channel: How can I add gravatar support in Confluence?