Different behavior of `quote_footer()` in beamer and html

[agricolamz]

I'd expected that pandoc will work inside the tufte::quote_footer(). But it didn't: it is aligned, but not converted.

---
output: 
  beamer_presentation:
    latex_engine: xelatex
    citation_package: natbib
bibliography: bibliography.bib
---

## title

> "Two equally interesting questions are at the heart of this book: how an extraordinary degree of idiosyncratic linguistic variation can coexist with an extraordinarily homogeneous speaker population, and how linguists might overlook the possibility of their coexistence."

> `r tufte::quote_footer(' [@dorian10: 3]')`

In .html version (i tried html_document, ioslides_presentation, slidy_presentation) citation is converted but not aligned:

---
output: html_document
bibliography: bibliography.bib
---

## title

> "Two equally interesting questions are at the heart of this book: how an extraordinary degree of idiosyncratic linguistic variation can coexist with an extraordinarily homogeneous speaker population, and how linguists might overlook the possibility of their coexistence."

> `r tufte::quote_footer(' [@dorian10: 3]')`

But it did work with the tufte::tufte_html: default output:

So I think, that it should be somehow written or changed here.

Here is the bibtex entry that I used:

@book{dorian10,
  title={Investigating variation: The effects of social organization and social setting},
  author={Dorian, Nancy C},
  year={2010},
  publisher={Oxford University Press}
}

> xfun::session_info('tufte')
R version 3.6.1 (2019-07-05)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Linux Mint 19, RStudio 1.2.1335

Locale:
  LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C               LC_TIME=ru_RU.UTF-8       
  LC_COLLATE=en_US.UTF-8     LC_MONETARY=ru_RU.UTF-8    LC_MESSAGES=en_US.UTF-8   
  LC_PAPER=ru_RU.UTF-8       LC_NAME=C                  LC_ADDRESS=C              
  LC_TELEPHONE=C             LC_MEASUREMENT=ru_RU.UTF-8 LC_IDENTIFICATION=C       

Package version:
  base64enc_0.1.3 digest_0.6.22   evaluate_0.14   glue_1.3.1      graphics_3.6.1 
  grDevices_3.6.1 highr_0.8       htmltools_0.4.0 jsonlite_1.6    knitr_1.26     
  magrittr_1.5    markdown_1.1    methods_3.6.1   mime_0.7        Rcpp_1.0.3     
  rlang_0.4.1     rmarkdown_1.17  stats_3.6.1     stringi_1.4.3   stringr_1.4.0  
  tinytex_0.17    tools_3.6.1     tufte_0.5       utils_3.6.1     xfun_0.11      
  yaml_2.2.0     

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