Re: Modes Question
You also have to consider the context you are playing in. You can swear you are playing D Dorian over a C Major chord all you want, but the net effect is that you are in C Major. Now if you introduced an F# (while soloing) on top of the C major chord, you are implying C Lydian (Harmonically spelled C, D, E, F#, G, A, B.)
Additionally, Diatonic refers to scale construction consisting of (for the most part), half or whole step intervals using sequential note letter names. (A, B, C, D, E, F# and so on...) Harmonic minor would be the intervallic exception here although it still does adhere to the sequential note letter names.
To contrast, a scale such as Major or minor Pentatonic has large intervallic leaps which not only are greater than half or whole steps, but omit actual scale (letter)degree names. Example:
C Major Pentatonic harmonically spelled C, D, E, G, A
(Relative minor) A minor Pentatonic A, C, D, E, G
Note the missing scale degrees from both and count the inervallic leaps between the E and G, and also between the A and C.