  In this paper, we study stability of $M$-compactness for $l^p$ sum of Banach
spaces for $1\leq p<\infty$. We also obtain a characterization of $M$-compact
sets in terms of statistically maximizing sequence, a notion which is weaker
than a maximizing sequence. Moreover, we introduce the notion of
$\mathcal{I}$-$M$-compactness of a bounded subset $M$ of a normed linear space
$X$ with respect to an ideal $\mathcal{I}$ and show that it is equivalent to
$M$-compactness for non-trivial admissible ideals.
