Reproduced on Crunchbang Waldorf, Inkscape trunk revision 12849, with "Scale stroke width" off.
Steps:
1. Open a template in mm (or the default EN template in px, and then change the default unit to mm).
2. Uncheck "Scale stroke width".
3. In the preferences of the Pencil tool, check "Use last style".
4. Draw a path with the pencil.
5. Set the path width to 1 mm.
6. Draw another path -> the width is 3.53 mm.
7. Set the path width to 1 px.
8. Draw another path -> the width is 3.53 px.
Reproduced on Crunchbang Waldorf, Inkscape trunk revision 12849, with "Scale stroke width" off.
Steps:
1. Open a template in mm (or the default EN template in px, and then change the default unit to mm).
2. Uncheck "Scale stroke width".
3. In the preferences of the Pencil tool, check "Use last style".
4. Draw a path with the pencil.
5. Set the path width to 1 mm.
6. Draw another path -> the width is 3.53 mm.
7. Set the path width to 1 px.
8. Draw another path -> the width is 3.53 px.