We have at least 3 different bolding styles in user activity lists

Since a picture is worth a thousand words, let me show you:

Screen_Shot_2016-10-20_at_17.37.32

So it seems a deleted branch name is <strong>:

Screen_Shot_2016-10-20_at_17.39.50

An accepted merge request is <strong> and since it's a link, it's black:

Screen_Shot_2016-10-20_at_17.40.09

An then a commented merge request is a simple link:

Screen_Shot_2016-10-20_at_17.40.26