OpenWebMail: French Language Makes Reading Area Too Wide

[Obius]

Using OpenWebMail in EuMX with English, there is a margin of some 9 fixed-width font-size-14-point characters on each side of the screen. In User Preferences, if I change the language from English to French, the reading area becomes wider, so much so that the rightmost 6 fixed-width font-size-14-point characters of each line disappear off the screen and cannot be read without scrolling. Out of curiosity, I tried a few other languages: some do that and some don't. French is one that does and is the language that I'd like to use.

My questions are:

1. Why would changing language change anything other than the names of things?

2. Is there a way to correct this (for French)? I look in User Preferences for a setting to change but see nothing suitable, and I can find no previous related forum posts.

Thank you.

[janusz]

I do not see this behaviour (FF35, Win7).