I’ve tested editing the same Word file in WinXP Word 2003.

I notice on Word the font Fira sans Semibold appears as a different font in the list, below fira sans. Your way of grouping them seems more logic and proper to me, but it doesn’t seem to be compatible :(

I use Windows and Fira family is neither in Windows nor in LO fonts.

And so what? 
A writing software must run with any font what that follow opentype format standards.
The time of only 4 styles for a font is finished. You must provide appropriate support for more extended font families.

I installed Fira Sans SemiBold from here: https://github.com/mozilla/Fira/blob/master/otf/FiraSans-SemiBold.otf

I modified the default paragraph style like mentioned in description.

After save and reload the style stays as SemiBold.

Arch Linux 64-bit, KDE Plasma 5
Version: 5.2.0.0.alpha0+
Build ID: 011e65c93053c88eb752e50ef47c69872608cbcd
CPU Threads: 8; OS Version: Linux 4.4; UI Render: default; 
Locale: fi-FI (fi_FI.UTF-8)
Built on March 22nd 2016

You have to install more than one style to see the bug.
for example at least the basic regular, italic, bold, bold italic.

(In reply to synthview from comment #5)
> You have to install more than one style to see the bug.
> for example at least the basic regular, italic, bold, bold italic.

Sorry, I forgot to mention I already had Regular, Light, Bold, Italic, Light Italic, Medium Italic and Bold Italic installed.

and if you install the whole family?
On my side I’ve tried many times and DemiBold was lost at each save in .doc format.

(In reply to synthview from comment #7)
> and if you install the whole family?
> On my side I’ve tried many times and DemiBold was lost at each save in .doc
> format.

You really have all the 64 styles installed?

I am a designer :p it doesn’t mean I use them all at a time of course

Now I tried with OS X, but SemiBold is not available in LibreOffice. I can see it in Font Book.

Right,
if you disable “medium” and “medium italic” and restart LibreOffice, you’ll see SemiBold again.

(In reply to Buovjaga from comment #10)
> Now I tried with OS X, but SemiBold is not available in LibreOffice. I can
> see it in Font Book.

Confirming, I can't see SemiBold either in LibreOffice

No repro, after de-activating the Fira fontweights in comment 11

Version: 5.3.0.0.alpha0+
Build ID: 4d49c9601c9b3e26a336e08e057d299895683480
Threads CPU : 2; Version de l'OS :Mac OS X 10.11.5; UI Render : par défaut; 
Locale : fr-FR (fr.UTF-8)


1) Create a new Writer document
2) Type some text
3) Right mouse button click on paragraph, choose Edit Style
4) Select Fira Sans SemiBold as font. Click on OK, and Apply. Quit dialog.
5) Save document.
6) Close LO, restart LO, re-open test document. Fira Sans SemiBold still default style font.

synthview: am I correct in my understanding of your comment in comment 7 that your actual problem is that the font weight isn't exported to DOC format ?

Please give precise instructions on how to reproduce, because I only tested against a Writer document.

Setting needinfo

*** This bug has been marked as a duplicate of bug 69254 ***

I can’t reproduce with 32 styles installed. Semibold shows up fine, and medium shows up with the fix for bug 147739 fixed.