### Bug description

I have the input below:

- if I  use markdown headings, the slide is not readable

![image](https://user-images.githubusercontent.com/30607/198874576-95d6c24b-b27c-468a-ab3a-fb5dfe39324f.png)

- if I use html headins, it's all ok

![image](https://user-images.githubusercontent.com/30607/198874589-db457c9c-b214-47b3-b298-4602ba76b128.png)

I think quarto should manage also the first kind of syntax.

I'm using quarto 1.2.251.

Distributor ID: Debian
Description: Pengwin
Release: 11
Codename: bullseye

```
---
title: "Hello world"
format:
  revealjs:
    slide-number: true
    preview-links: auto
    theme: [dark]
    navigation-mode: vertical
    center-title-slide: false
    chalkboard: true
---

# Using Markdown headings

:::: {.columns}

::: {.column width="50%"}
## Colonna 1
:::

::: {.column width="50%"}
## Colonna 2
:::

::::

# Using HTML headings

:::: {.columns}

::: {.column width="50%"}
<h2>Colonna 1</h2>
:::

::: {.column width="50%"}
<h2>Colonna 2</h2>
:::

::::
```

### Checklist

- [X] Please include a minimal, fully reproducible example in a single .qmd file? Please provide the whole file rather than the snippet you believe is causing the issue.
- [X] Please [format your issue](https://quarto.org/bug-reports.html#formatting-make-githubs-markdown-work-for-us) so it is easier for us to read the bug report.
- [X] Please document the RStudio IDE version you're running (if applicable), by providing the value displayed in the "About RStudio" main menu dialog?
- [X] Please document the operating system you're running. If on Linux, please provide the specific distribution.
2022-10-30T10:49:49Z
aborruso
bug
closed
revealjs vertical slides: columns settings does not work well
https://github.com/quarto-dev/quarto-cli/issues/3111