The best module documentation I've found comes shipped with the SideviewUtils app. It describes ViewstateAdaptor at http://localhost:8000/en-US/modules#Splunk.Module.ViewstateAdapter as:
Injects settingsMap settings contained within a viewstate set into the current module branch
Parameters
savedSearch
(no description available)
suppressionList
(no description available)
viewstateId
(no description available)
Defined in $SPLUNK_HOME/share/splunk/search_mrsparkle/modules/results/ViewstateAdapter.js
This is not a good example (other modules are much more complete), but it tells you where the code is, which is always the most accurate documentation.
As for your XML header question, I couldn't see any bolded text.
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