Did postal censors ever add personal notes to the recipients, in the mail they censored?

OP here. I know a circumstance where it’s happened, and why; I was curious whether it was really a one-off.

Ludovik Zamenhof, son of a czarist censor, invented Esperanto, and maintained a voluminous international correspondence in Esperanto throughout his life.

When WWI started, everyone’s mail in the Russian Empire was subject to censorship, and Zamenhof’s was not going to be an exception. So an Esperantist had to be found to censor Zamenhof’s mail overseas.

Now, the Esperanto community is reasonably small, and it would be unlikely for an Esperanto-speaking censor in St Petersburg not to be familiar with the recipients of the mail. And given the good feelings between Esperantists, it’s not that surprising that the censor, Efstafeyev (sp?), would add in the margins his own curt little greetings to the recipients.

If you’re going to have your mail censored, that’s probably as good an arrangement as any.

Predictably enough, it didn’t last. Soon enough, Efstafeyev apologetically adds the marginal comment that from now on, all correspondence with Zamenhof has to be in a mainstream language like German or French. His superiors presumably thought the arrangement a bit too cozy…

(So when Zamenhof was trying for his translation of the Bible to be published in England, he had to write in French—and he couldn’t mail the manuscript at all: it was only possible to send it out of Warsaw after the war, and Zamenhof’s death: De Kembriĝo ĝis Edinburgo – 20 jarojn por la Esperanta Biblio (1).)