A possible exception to this rule of "etiquette"
It might be that within the conversation on one thread, there is an important aspect that can best be looked at on a specialised board, such as "Handwriting Deciphering & Recognition"
In this case, the person posting needs to link the main thread and make it clear that the deciphering question is part of an existing query.
As mentioned straight out duplication is not a good idea.
Sue