In the 2019 VS SDK, the CompletionItem class (from the namespace Microsoft.VisualStudio.Language.Intellisense.AsyncCompletion.Data, assembly Microsoft.VisualStudio.Language.dll) has a property called InsertText that should define the text to be inserted when commiting this suggestion/CompletionItem.
However, the current behavior is that this property doesn't seem to be used and the text inserted is the DisplayText property. The DisplayText property should only define what is seen in the UI, as per the doc.
I'm getting this behavior with the sample code found here and with an extension I'm writing (extending Intellisense for C#).
I would like to be able to have the DisplayText different of the InsertText, so the DisplayText can contain some small bonus info inside parentheses for example.