Are there any good points to annotate for Sebastian's speech in act 4, scene 3 of Twelfth Night?

Act 4, scene 3 is a very brief scene; in fact, it seems to exist purely as a vehicle for this soliloquy from Sebastian, highlighting its significance. Sebastian is in Olivia's garden; we, the audience, know this, but Sebastian, who refers to her only as "the lady," we may infer knows little about her, possibly not even her name.
Notable in this soliloquy is the number of times "madness" is discussed. Sebastian declares that "wonder," rather than "madness," has overtaken him, but he then questions himself, as "my soul disputes well with my sense." He even ponders whether "the lady" might be mad, rather than Sebastian himself, but dismisses this notion as a mad person would not be able to "sway her house, command her followers," and conduct herself in such a "stable" fashion.
Sebastian's soliloquy is in verse, but does not contain any rhyme. It is interesting that the last four lines of the scene—two from Sebastian, and two from Olivia—are rhyming couplets. This suggests a level of unity between Sebastian and Olivia which stands in contrast to the blank verse of the initial soliloquy, at times almost incoherent in its cyclical repetition of the same concern. Upon Olivia's arrival, Sebastian goes from hovering on the brink of "madness" to "truth" and being "true." This may indicate that Sebastian has found his true purpose in accompanying Olivia, the lady who is the subject of his thoughts.