Microtypography protrusion with Polish quotation marks

Use T1 fontencoding instead of OT4 (default).

\documentclass{article}
\usepackage[T1]{polski}
\usepackage[utf8]{inputenc}
\usepackage{microtype}

\begin{document}

\noindent
``Lorem'' \newline
,,Lorem'' \newline
Lorem \newline
ć, ń, ó, ś, ź, ż, ą, ę, ł \newline
Ć, Ń, Ó, Ś, Ź, Ż, Ą, Ę, Ł

\end{document}

EDIT: This has been fixed in version 2.7b (28 Feb 2019).

---

The default microtype configuration lacks protrusion settings for the „ ligature. You can add them like this (in the preamble):

\LoadMicrotypeFile{cmr}
\SetProtrusion
   [ name     = cmr-OT4,
     load     = cmr-OT1]
   { encoding = OT4,
     family   = cmr  }
   {
      "FF = {500,300}
   }