It’s a known issue Yjs doesn’t persist marks on nodes which ProseMirror allows you to do. Safest bet at the moment is to use attributes instead.
@TeemuKoivisto Can you elaborate more on this, or point me to an existing issue?
              
              
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          thanks @TeemuKoivisto, this is very helpful
              
              
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          Still no update on this issue? It is really needed.