According to the Activity Vocabulary specification, the summary property should be HTML encoded, but #Mastodon is putting plain text in the summary property. #Hollo is putting #HTML in the summary, but should I change Hollo's behavior? 
https://www.w3.org/TR/activitystreams-vocabulary/#dfn-summary
Activity Vocabularyの仕様によると、summaryプロパティはHTMLでエンコードされなければならないそうだが、Mastodonはsummaryプロパティに平文のテキストを使用している。HolloはsummaryにHTMLを入れているが、Holloの動作を変える必要が有るのだろうか？ 
https://www.w3.org/TR/activitystreams-vocabulary/#dfn-summary
QT: https://fosstodon.org/@hongminhee/113276538710999787 [参照]
According to the Activity Vocabulary specification, the summary property should be HTML encoded, but #Mastodon is putting plain text in the summary...
