Unexpected behavior when trying to enforce sentence-style headings -- user error, or bug?

[emteelb]

I have some confusion about implementing a style rule to enforce sentence-style headings. I am unsure if I am just missing something in trying to implement a style rule, or if my testing shows a Vale limitation or bug?

Given the following Vale style rule for trying to enforce sentence style headings, inspired by an example within Vale documentation:

---
extends: capitalization
level: warning
match: $sentence
message: "Use sentence-style capitalization in '%s'. Refer to https://capitalizemytitle.com/style/SentenceCase/ to generate."
scope:
  - heading.h2
  - heading.h3
  - heading.h3
  - heading.h4
  - heading.h5
indicators:
# `indicators` is an array of suffixes that indicate the next token
# should be ignored. By using an indicator, ":", this rule will ignore
# a capitalized letter after a colon in a heading, for example
# "Creating secure systems: How to implement traffic encryption"
  - ":"

Also given the following Markdown file with some example headings:

# Test Article on a Subject of Great Interest

## Using Zebra to provision the environment

### Using correct Rhinoceros syntax

### Using Lion in Heterogeneous Environments

## More information about Jackal deployments

When running Vale, vale version v3.7.0, I expect all of those headings, except the title, to trigger warnings. However, only two of them do:

5:5  warning  Use sentence-style capitalization in
              'Using correct Rhinoceros syntax'. Refer to
              https://capitalizemytitle.com/style/SentenceCase/
              to generate.
7:5  warning  Use sentence-style capitalization in 'Using
              Lion in Heterogeneous Environments'. Refer to
              https://capitalizemytitle.com/style/SentenceCase/
              to generate.

Vale Studio link: https://studio.vale.sh/s/f5cda2da54aadd859828c2cb9d995dc2

[emteelb]

Goofing around, adding threshold: 0.9 to the rule, correctly triggers warnings for all four headings. Changing the threshold value to 0.7 only triggers a warning for the heading "Using Lion in Heterogeneous Environments".

https://studio.vale.sh/s/9044d33789daa3e81516df254c5077d8

From Vale documentation for the capitalization extension:

threshold float The minimum proportion of words that must be (un)capitalized for a sentence to be considered correct (default: 0.8).

For this particular file, 0.9 is a working threshold. I am not sure what value I would generally want though for this rule. 1.0? 0.99? Something else?

[jdkato]

1.0 would be the strictest setting and will likely require appropriate use of a vocab to avoid false positives related to branding/company-specific terms.