Oh Salesforce… That’s right, all the normal techniques go right out the window when talking about Tasks and Activities. We laugh about Salesforce standard objects being completely custom, and their custom objects being completely standard…
You may be able to use a Text Field on the discussion object and mark it as an External ID. Then in your Skuid pages you’ll have to set that text field to be the value of the Task ID you are adding Discussion comment to. And when you query your Discussion comments - you’ll just filter the External ID field by the value of the Task ID.
There are downsides to this. Reporting will be hard. This relationship wont be indexed and if you’ve got millions of tasks performance will be challenging.
But regardless of how you present this in Skuid - I think you are going to have to do somthing like this in your Salesforce data model in order to allow more than one comment to be added to a given task.