Having the same name in the menu is a WF to me. We should rather think to give items speaking names like 'Roman Number' instead of an anonymous numbering (same as for colors). It doesn't matter too much what name it gets, 'LibreOffice Style' would work.

(In reply to Harald Koester from comment #0)
> In Writer for the following styles different terms are used in the menu
> Styles:
> (1) Paragraph style “Default Style”, menu: “Default Paragraph”
> (2) Character style “Default Style”, menu: “Default Character”

They have the same name in the sidebar, as they are not on a single tab of the styles deck, so its easy to differentiate them there, but in a single menu, its important for them have different names to easily know the paragraph styles from the character styles.

> (3) List style “List 1”, menu: “Bullet List”
> (4) List style “Numbering 1”, menu: “Number List”
> (5) List style “Numbering 4”, menu: “Roman List”

Styles menu will have more descriptive names which would be easier to understand, specially for beginners, while the sidebar will be having names like Numbering 123, and Numbering IVX (bug 106988).

(In reply to Yousuf Philips (jay) from comment #2)
> (In reply to Harald Koester from comment #0)
> > In Writer for the following styles different terms are used in the menu
> > Styles:
> > (1) Paragraph style “Default Style”, menu: “Default Paragraph”
> > (2) Character style “Default Style”, menu: “Default Character”
> 
> They have the same name in the sidebar, as they are not on a single tab of
> the styles deck, so its easy to differentiate them there, but in a single
> menu, its important for them have different names to easily know the
> paragraph styles from the character styles.

I'm sorry Jay, I don't agree. Using different terms for the same thing is always confusing. Particulary if we promote the use of styles, it is necessary that a user is able to recognize at first glance, that the same styles are meant in these cases. For me it was hindering and I think for other users it's still hindering if they have to check this first. 

> 
> > (3) List style “List 1”, menu: “Bullet List”
> > (4) List style “Numbering 1”, menu: “Number List”
> > (5) List style “Numbering 4”, menu: “Roman List”
> 
> Styles menu will have more descriptive names which would be easier to
> understand, specially for beginners, while the sidebar will be having names
> like Numbering 123, and Numbering IVX (bug 106988).

Of course more descriptive names are a good thing, but these names should be used everywhere in the user interface.

Seems to me there are some grounds here.

(In reply to Harald Koester from comment #0)
> In Writer for the following styles different terms are used in the menu
> Styles:
> (1) Paragraph style “Default Style”, menu: “Default Paragraph”
> (2) Character style “Default Style”, menu: “Default Character”
I don't agree on this, looks logical as a general name. 

> (3) List style “List 1”, menu: “Bullet List”
Actually it's a problem of "List 2" style names. Can't say what's the perspective. Bug 106988 is so far for numbering styles. Bug 83362 would help.
Some rename here would help.

> (4) List style “Numbering 1”, menu: “Number List”
> (5) List style “Numbering 4”, menu: “Roman List”
Jay made changes in  Bug 106988 that are for better. But when I pay attention to menu items here in menu Styles, I'd agree that some unification could be useful.
It's "Alphabet Uppercase List" in Style menu and "Numbering ABC" in Sidebar and Numbering Style. I don't like it being different. "Numbering ABC" was sufficient enough. "Alphabet Uppercase List" would better be "Alphabet Uppercase Numbering ABC" or simple "Numbering ABC". It's not a general name but the same style. 
Please comment on this one. And please "See Also" bug where this was changed. 

> distinguish these styles: the style category could be put in brackets after
> the style name in the menu, e. g. “Default Style (paragraph)” or “Numbering
> 1 (list)”. 
Wouldn't agree because it should be clear and for space. 

> create sub-menus for each style category in the Style menu.
I'd agree on this one. Why would there be single Bullet List and 5 Numbering Lists? Submenus with all lists available in Sidebar List Styles would be better. 
I'd propose this bug be first about this.

Checked again with version 6.4.2 (Win10):

(1): A default style is no longer provided in the menu: OK now.
(2): Character style “Default Style”, menu: “Default Character”: No change. Style name is still different!
(3): List style "Bullet •", menu: “Bullet List”: Style name has changed. Style name is still different!
(4): List style “Numbering 123”, menu: “Number List”: Style name has changed. Style name is still different!
(5): List style “Numbering IVX”, menu: “Roman Uppercase List”: Both names have changed. Style name is still different!

New Cases with different style names:
(6) List style “Numbering abc”, menu: “Alphabet Lowercase List”
(7) List style “Numbering ABC”, menu: “Alphabet Uppercase List”
(8) List style “Numbering ivx”, menu: “Roman Lowercase List”

Checked with version 7.0.0 (Win10). 

These style names are still different:
(1) Character style “Default Character Style”, menu: “Default Character”
(2) List style "Bullet •", menu: “Bullet List”
(3) List style “Numbering 123”, menu: “Number List”
(4) List style “Numbering abc”, menu: “Alphabet Lowercase List”
(5) List style “Numbering ABC”, menu: “Alphabet Uppercase List”
(6) List style “Numbering ivx”, menu: “Roman Lowercase List”
(7) List style “Numbering IVX”, menu: “Roman Uppercase List”

Also persons who need a screen reader have difficulties with the styles menu:
At first they can't distinguish between the styles "Quotations" and "Quotation". Furthermore the can't recognize the separator lines between the different style groups. So they don't know which kind of style they have just selected.