"dear comrade" is correct and usable in written English.
It can be used in formal and informal contexts, usually to address someone with whom the speaker or writer has a strong relationship, such as a close friend, family member, or colleague. For example, one might write, "Dear comrade, I hope this email finds you well."
Caught in an ambush, he was left cradling a dear comrade as he lay fatally wounded.
In March 1923, Lenin sent Stalin the following letter: "Dear comrade Stalin!
Agamemnon is mad with rage and knows not how to look before and after that the Achaeans may fight by their ships in safety". Patroclus did as his dear comrade had bidden him.
I am not a political analyst, but I am now driven to ask: Dear Comrade President, don't you think your continued stay as President will only serve to deepen the crisis of confidence in the government of the country?
And he continued to the end to hold in deep affection such people as Joe Slovo, the chairman of the party, who was to him "dear comrade, dear brother, dear friend", but to his opponents the "KGB general .Mr Mandela insisted he was not a communist, though.
"Dear Comrade Xi Jinping, we are loyal Communist Party members," it begins, and then cuts to the chase.
Andrei Voznesensky, poet Honoring Pasternak Dear comrades, brothers in the long-suffering task of literature.
Yes, dear comrades, it might be true, even though it was an American who said it.
I hate these Hutus who can be brought to kill and who, I swear to you, kill Hutus, dear comrades.
Dear comrades, you know that the day before yesterday, on Sunday, my meeting with the President of the United States, Ronald Reagan, has been completed in Reykjavik, Iceland...
The song lists the types of Hutus the singer detests: I hate these Hutus, these de-Hutuized Hutus, who have renounced their identity, dear comrades.
