inflectional or derivational suffix?

[Fame]

-->inflectional (grammatical) (e.g. –ed, -ly, -‘s, -s, -er, -ed, -es, -est, -ing: if it is used to turn a verb into e.g. present participle: example: break -->breaking, eat-->eating)

-->derivational (lexical): words formed by the attachment of lexical affixes are derived from other words, and derivational affixes are those affixes which help in this derivation (e.g. dis-, re-, in-, be-, en-, -ly, -ance, -able, -ize, -ish, -like, -ment, -ing: if it is used to turn the verb into a noun: example: build --> a building, two buildings, nourish-->nourishing)

I know sometimes when a word carries inflectional or derivational suffix, but sometimes it's a bit confusing. Please help confirm if I'm correct with these examples(inflectional is in bold, derivational underlined):
1. He participates quite happily in the communal walks.
2. For some time I have known of her insensitivity to my feelings.

[Raymott]

-->inflectional (grammatical) (e.g. –ed, -ly, -‘s, -s, -er, -ed, -es, -est, -ing: if it is used to turn a verb into e.g. present participle: example: break -->breaking, eat-->eating)

-->derivational (lexical): words formed by the attachment of lexical affixes are derived from other words, and derivational affixes are those affixes which help in this derivation (e.g. dis-, re-, in-, be-, en-, -ly, -ance, -able, -ize, -ish, -like, -ment, -ing: if it is used to turn the verb into a noun: example: build --> a building, two buildings, nourish-->nourishing)

I know sometimes when a word carries inflectional or derivational suffix, but sometimes it's a bit confusing. Please help confirm if I'm correct with these examples(inflectional is in bold, derivational underlined):
1. He participates quite happily in the communal walks.
2. For some time I have known of her insensitivity to my feelings.

"The distinction between inflection and word-formation [derivation] is not at all clear-cut. There are many examples where linguists fail to agree whether a given rule is inflection or word-formation. The next section will attempt to clarify this distinction." Look here:
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)