Q:

Is it appropriate to flag feature requests to get attention from CMs?

I have seen some feature requests that have no involvement by a CM on the post (no comments, no answers, no edits). It may be possible that they have not seen that feature request. In such case, would it be appropriate to flag as "in need of moderator attention" saying "This feature request needs your attention".

A:

No. Flags are kind of like yelling FIRE. 
From experience, CMs/Devs/PMs and probably other employees do keep an eye on meta - both main and per site, and while they might not always answer, are probably aware.
Flags are for things that need (semi) immediate attention, which FRs never are.

