Morphology (linguistics - Wikipedia, the free encyclopedia)
Note that you've given "ing" as both an inflectional as well as a derivational suffix.
Any suffix that transforms a base word, such as "know" into a different tense, etc. without changing the meaning of the underlying word is inflectional. So an inflectional change for grammatical purposes in inflectional.
If you are forming a new word, with a different underlying meaning from the base word (ie. not simply for grammatical correctness) you're adding a derivational suffix.
Consider "feelings". The base word is "feel". I would call the "ings" derivational because "feelings" is a different word. This contrasts with "feeling" as the present participle of "feel". Here the "ing" is inflectional.
Here's my guess: Blue - inflectional, Red - derivational.
1. He participatesquite happily in the communal walks.
2. For some time I have known of her insensitivity to my feelings.
common -> commune (derivational) -> communal (inflectional)
sense -> sensitive (derivational) -> insensitive (derivational) -> insensitivity (inflectional)