Default font is causing impersonation problems
This suggestion is based on PositiveIona's idea at https://twitch.uservoice.com/forums/933812-safety/suggestions/44529945-sans-serif-fonts
However, the suggestion to use serif-fonts to resolve the lower case 'l' vs upper case 'I' problem (to clarify the first one is an 'L' and the second one is an 'i') will make the platform less accessible for certain people, ESPECIALLY those with dyslexia. So you'd just be replacing one problem with an entirely new one.
I'd like to propose that, instead of adding serifs, we should find a font that distinguishes the letters more clearly whilst still being sans-serif.
Some examples include: Verdana, Tahoma, Trebuchet, or Open-Dyslexic; though I'm sure many more exist.
I agree with PositiveIona that we do need a fix to the problem of people impersonating other users by switching lower case 'L' and upper case 'i' with each other. But switching to a serif font as they propose will create more problems than it solves. Please consider switching to a more accessible font that still resolves this issues such as one of the examples listed above.