+++ codinghorror [Oct 09 14 04:55 ]:
I have never, ever seen anyone use (1) to make a list on Stack Overflow, or any Stack Exchange site, or Discourse.
But I see people try (and fail) to use 1) to make lists pretty much every single day.
Perhaps the (1) style is less common. But remember, techy web forums are not the only users to consider. Lots of people are using Markdown now for scholarly writing, legal writing, journalism, etc. And (1) is used in many contexts. In linguistics, for example, numbered examples are nearly almost numbered that way: here’s one example. This style is right there in the Chicago Manual of Style alongside the others. I use it all the time. Here is an example from the Chicago Manual of Style illustrating various styles of list numbering that are in use:
I. Historical introduction
II. Dentition in various groups of vertebrates
A. Reptilia
1. Histology and development of reptilian teeth
2. Survey of forms
B. Mammalia
1. Histology and development of mammalian teeth
2. Survey of forms
a) Primates
(1) Lemuroidea
(2) Anthropoidea
(a) Platyrrhini
(b) Catarrhini
i) Cercopithecidae
ii) Pongidae
b) Carnivora
(1) Creodonta
(2) Fissipedia
(a) Ailuroidea
(b) Arctoidea
(3) Pinnipedia
c) Etc. . . .