Conformity is a virtue, creativity suspect, humor forbidden, and voice mute.
This isn't a list describing "conformity", it is a list of things about legal writing.
- Conformity is a virtue.
- Creativity is suspect.
- Humor is forbidden.
- Voice is mute.
I think the 4th part might not be clear. The word "voice" here is referring to the author's "voice" or their unique style of writing that shows their personality. The Grammar Girl website has more information about Voice and Tone in Writing:
Voice is the distinct personality, style, or point of view of a piece of writing or any other creative work. Voice is what Simon Cowell is talking about when he tells "American Idol" contestants to make a song their own and not just do a note-for-note karaoke version.
That sort of individual personality is not acceptable in legal writing according to your sentence. Authors should "mute" their own voice and conform to a consistent tone and style. As user151841 pointed out in a comment: "Ideally, with legal writing, you wouldn't be able to tell who wrote it."
One clue that this list of items isn't describing conformity is that the last 3 items don't match the first item in structure. Writers tend to use parallelism when writing lists. Many style manuals state that when writing lists "all items should be syntactically and conceptually parallel". An example of parallelism where each item in the list is describing the first word is :
Flying is fast, comfortable, and safe. (Source)
You could expand the list like this:
- Flying is fast.
- Flying is comfortable.
- Flying is safe.
If we try to do that with the "conformity" sentence, it doesn't make sense:
- Conformity is a virtue.
- Conformity is creativity suspect.
- Conformity is humor forbidden.
- Conformity is voice mute.
Items 2, 3, and 4 don't match the first one in structure, and the word order seems strange. Normally we would expect something like "Conformity is very dull." so "creativity suspect" doesn't make much sense unless we're reading something poetic instead of something literal. So that interpretation seems like it doesn't fit the context and it doesn't have the parallelism we would normally expect of something carefully written and edited.
Another way to write the sentence in your question:
In legal writing, conformity is admired, creativity suspect, humor forbidden, and voice suppressed.