When a modal HUD is shown (i.e. “Posting Comment”), the status bar turns black. Because the navigation bar on top is dark blue, the status bar is harder to see. When the HUD disappears, the status bar becomes the normal color again.
This will be fixed in the next version of the app.
A full writeup of the problem and solution are here: Presenting a view controller without changing the status bar color, like UIAlertController