Affected versions

• Latest Nightly 88.0a1
• Firefox 87.0b8
• Firefox 86.0

Affected platforms

• Windows 10 64bit
• macOS 11.3
• Ubuntu 20.04

Steps to reproduce

1. Start Firefox
2. Open the following URL: https://en.wikipedia.org/wiki/Firefox
3. Select the following italic text: "This article is about the web browser." from the start of the article
4. Right click the selected text
5. Select Print Selection

Expected result

• Print preview shows the selected text

Actual result

• Print preview is blank also after printing, the page will be also blank

Regression range

• This is not a regression, I can reproduce from the moment the option to Print Selection was implemented in context menu: bug 140718

Suggested severity

• Since this might be specific to Wikipedia or other particular webpages or textareas and has been here a long time, I would not mark it as a high severity thus marking it as S3

This is not a bug; that text is styled with class=hatnote on the wikipedia page, and their CSS includes a print-media rule that hides it:

@media print {
 .ns--1 .ambox,
 .ns-0 .ambox,
 .ns--1 .navbox,
 .ns-0 .navbox,
 .mediawiki.ns--1 .mw-parser-output .sidebar,
 .mediawiki.ns-0 .mw-parser-output .sidebar,
 .ns--1 .sisterproject,
 .ns-0 .sisterproject,
 .ns--1 .hatnote,
 .ns-0 .hatnote,
 /* ...snipped a bunch more selectors... */
 .nourlexpansion a.external.text:after,
 .nourlexpansion a.external.autonumber:after {
  display:none !important
 }

So that note (along with various other navigation-related and cross-referencing content) is intended to be displayed on-screen only, not included in printed output.