Hi. To provide an onClick xp:eventHandler for the summary column, you can provide the summary facet, containing the link to appear in the summary column. The code would be roughly like so:
title="Some Title"
text="#{javascript:viewEntry.getColumnValue('Topic');}">
value="#{javascript:viewEntry.getUniversalID()}">
If we provided an onClick property in the xe:summaryColumn complex-type, then it could only be used to provide a snippet of client-side JavaScript to execute, not a full XPages event, because it's not possible to associate an eventHandler with a complex-type property. So I don't think it's useful to provide a limited onClick event there. Instead, if you need to customize the column, use the "summary" facet, as indicated above.
As you've said, we should provide a title property for the xe:summaryColumn, and for the other column objects used with the xe:dataView. I've logged an SPR to track that issue:
SPR#MKEE8YNECY XPages, xe:dataView, summary column doesn't have "title" property