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The various Unicode characters for phi (Φ or φ or ϕ) display inconsistently between body and preview in Google Chrome.

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In particular, φ &phi and ϕ &#981 display reversed. It's obviously difficult to tell which (if either) is incorrect!

On its own, this isn't too much of an issue. However, when used in conjunction with phi characters in a MathJax equation (\phi \varphi), the result can be very confusing.

See this answer where I originally noticed the difference. Depending on whether you are editing or viewing, the variables in the equation have their definitions swapped!

I understand this is a well-documented problem when displaying between platforms, but as another example, all three characters display inconsistently between the iOS App, iOS Safari and Google Chrome (all the other Greek characters appear to display much more consistently).

Compare:

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Screenshots from this post.

Platforms:

  • Google Chrome: Version 68.0.3440.106 on Windows 10, version 1803
  • iOS:
    • Device: iPhone 5S (Global)
    • iOS Version: Version 11.4.1 (Build 15G77)
    • App Version: 1.6.6.2
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  • 3
    Reproducible in Firefox Nightly 63.0a1, Arch Linux with Gnome 3.28.
    – Sebastian Simon
    Aug 10, 2018 at 15:12
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    Why are you sure this is an app or SE bug, rather than just a difference in fonts, which is where my first inclination runs?
    – Jeff Zeitlin
    Aug 10, 2018 at 15:13
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    Stack Exchange uses the font Consolas for monospace text. This is the font that swaps phi and varphi.
    – Sebastian Simon
    Aug 10, 2018 at 15:25
  • @JeffZeitlin you're right - I realise it's a difference between the two typefaces in body and preview, but I think we can all agree it's confusing to have the two characters swapped on the same page.
    – Jack
    Aug 10, 2018 at 15:46
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    @Jack: But if it's a problem with the fonts, there's nothing SO can do about it.
    – Nicol Bolas
    Aug 10, 2018 at 17:09
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    @NicolBolas Agreed, but there may potentially be other solutions. Either way, I feel it's still worth identifying as a piece of unexpected behaviour.
    – Jack
    Aug 10, 2018 at 17:17
  • 3
    Phi, phi, fo, fum .....
    – Rosinante
    Aug 11, 2018 at 23:28
  • @NicolBolas they could use a different monospace that doesn't have inconsistencies with the font used for display.
    – Cave Johnson
    Jun 13, 2020 at 15:09

1 Answer 1

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According to "Writing mathematical expressions" by Jukka K. Korpela, page 128:

for [unspecified] historical reasons [...] many fonts have [φ and ϕ] reversed, such as Calibri, Consolas, Lucida Sans Unicode, Palatino Linotype, and Symbola. This means that its generally very risky to use φ and ϕ in different meanings.

Therefore, SE requires a feature that warns users when they use both symbols in the same post.

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  • The first half of this post is good, the second part would be a feature request (which I would disagree with). Feature requsts should be made in their own questions.
    – Luuklag
    Jun 13, 2020 at 10:00
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    @Luuklag OK, I posted it as an own question: meta.stackexchange.com/questions/349370/…
    – root
    Jun 13, 2020 at 14:09

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