The rtBlock contains rtRawCD as a content. If rtBlock record is present it represents the unsupported record type.
Domino groups records in blocks (using CDBEGINRECORD and CDENDRECORD elements). rtBlock corresponds to such a grouping. rtContainer method getRichTextItem retrieves a collection or rtRawCD class objects corresponding to all CD-records in item record groups between CDBEGINRECORD and CDENDRECORD that are converted to rtBlock objects with all records ( rtRawCD objects) in between them stored as rtBlock Content.
Few record types are not supported, also new Domino version may bring new structures - all these remain as rtRawCD and rtBlock objects and can be deleted or moved to other place.
rtBlock elements should not be used when creating rich text item content as they get created implicitly creating appropriate structures.
However one should be aware of their existence when accessing rtContainer content.
ctx.getRichTextItem doc, "Body"
set enum = new rtCollection(ctx.All)
do while enum.hasMoreElements
if enum.nextElement isA "rtBlock" then
Print "block for ", SignatureTypeTable(enum.currentElement.Signature)