Adding DISTINCT to the query will give you the results required as per the spreadsheet.

Two observations.

1. CaseID has different data type in the two tables, presume this is a typo!

2. The query has no ORDER BY. The TOP 50 you slelect could be any 50 rows, is this correct?

p.s. Also noticed your WHERE clause is is ignoring comments containing the text 'null', is this correct or are you really trying to ignore comments containing null, the two are not the same.