Numbered list is not displaying properly. Is this a StackExchange bug?

It actually appeared weird in a different way for me, likely due to my system:

The underlying problem being that a numbered list was nested inside a bulleted list:

- 1a. The larger the ratio of known to unknown letters, the easier
- 1b. The more contiguous known letters you have, the easier
- 2. The more candidate words you have (2 being the fewest), the easier
- 3. The larger the pool of 'candidate words' for any pattern, the harder
- 4. Finally, the more unusual the letters or patterns, the easier the puzzle (which is linked to #3 of course)
- 5. Having the first letter a 'known' letter makes the puzzle easier

Items 2-5 were detected as a numbered list and the system tried to display them as such. 1a and 1b were fine because the letter prevented auto-conversion to a numbered list.

Unfortunately, this kind of nested list, where there's nothing except the nested list item within the outer list item, is sort of undefined behavior on Stack Exchange. If you want to nest lists, you need to put something that's not a new list on the outermost layer. Each list item needs content to itself. This is why when I fixed the list by getting rid out the outer bulleted list, then switching 1a/1b to be an inner bulleted list, I had to add content at the top-level for item 1:

1. known letters:
    - 1a. The larger the ratio of known to unknown letters, the easier
    - 1b. The more contiguous known letters you have, the easier

Omitting the "known letters:" bit would have resulted in wacky formatting.

Note you can always try to diagnose/fix problems with the Markdown yourself if the rendering seems funky, simply via attempting to edit the post.