User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:81.0) Gecko/20100101 Firefox/81.0

Steps to reproduce:

Set gfx.webrender.enabled to true

Actual results:

Fonts become thin and ugly in Firefox on some websites and in Firefox UI.
Screenshots with enabled/disabled webrender: https://yadi.sk/d/e9QwKTqasG-8Rg?w=1

Expected results:

No difference

Laptop Dell Inspiron 3542 (Intel Core i3 4005U, integrated video Intel(R) HD Graphics Family).
CPU-Z exported report: https://yadi.sk/d/JkUO0kztU1vE8g

Troubleshooting info (exported from about:support): https://yadi.sk/d/al8gg_eERmJR_Q

I'm sorry for sharing info/screenshots in cloud storage, but i see no different way.
Consider downloading screenshots and comparing them in fullscreen mode to feel the difference.

Yep, the difference looks quite obvious to me. It seems like the gamma is different or something. Can you check if Chrome matches Firefox with WebRender enabled or with WebRender disabled?

Your ClearType parameters are: Gamma: 2.2 Pixel Structure: RGB ClearType Level: 100 Enhanced Contrast: 200 where as I have Gamma: 1.8 Pixel Structure: RGB ClearType Level: 100 Enhanced Contrast: 50 so maybe we're not respecting Enhanced Contrast properly

Screenshots of bugzilla page (Chromium, FF wr enabled, FF wr disabled): https://yadi.sk/d/1yxIlHH8pyEqNw?w=1

Can you share the values you have in the registry in Computer\HKEY_CURRENT_USER\Software\Microsoft\Avalon.Graphics*?

[HKEY_CURRENT_USER\Software\Microsoft\Avalon.Graphics]

[HKEY_CURRENT_USER\Software\Microsoft\Avalon.Graphics\DISPLAY1]
"PixelStructure"=dword:00000001
"GammaLevel"=dword:00000898
"ClearTypeLevel"=dword:00000064
"EnhancedContrastLevel"=dword:000000c8
"GrayscaleEnhancedContrastLevel"=dword:000000c8
"TextContrastLevel"=dword:00000001

ClearTypeLevel=100
EnhancedContrastLevel=200
GammaLevel=2200
GrayscaleEnhancedContrastLevel=200
PixelStructure=1
TextContrastLevel=1

When I set my machine to the same settings I don't see the same difference that you do.

From looking at your screenshots it looks like Firefox with WebRender enabled has the same font rendering that Chrome does. Would you agree?

Almost, but in ff with enabled webrender thin fonts are more contrast/saturated.
Compare my YouTube screenshots (look at left sidebar with "Home", "Trending", "Subscriptions"): https://yadi.sk/d/x40GPHgVIiZ8nA?w=1

But i do like the way how fonts (especially thin) rendered with disabled wr (more "fat", "smooth", contrast and easier to read). I don't like chromium/webrender "style".

That's one of the reasons i prefer FF.

Are you able to compare with Edge? (Ideally both the Chromium based and the non Chromium based one)

I have no idea how to get the old Edge
Chromium, Edge (chromium based), FF (wr enabled/disabled): https://yadi.sk/d/Ph7h_oUSYCyCmw?w=1

Still actual issue
https://disk.yandex.ru/d/iAwM0eY4q_ldCg