This is a really good point. My wife and I produce a history podcast where, right now, a lot of it draws on primary sources such as letters, diaries, etc. from the late 1800's to early 1900's. The ones in German she translates into English, but it feels "wrong" to change someone's words that are already in English.

The net result is that it's easier (for me) to understand a letter written by someone in a translated foreign language than one written by someone in English from the same period.