The answer is yes for the first message of a conversation, but not for the comments or as a reassignment of the full original conversation to another subject.

Combining multiple subjects for a same message, or using only one subject allows for the same capabilities:

You can click the 3 vertically-aligned-dots on the conversation and then on "Post on other subjects":

This will create a new conversation you can comment and that embeds the first message of a conversation. You can post it on any other subject(s) from any of the workspaces you are member of.

You can then remove the first message using the x (only available if it's your message)

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