Mute these words in your settings here: https://twitter.com/settings/muted_keywords
ActivityTweet
generic_activity_highlights
generic_activity_momentsbreaking
RankedOrganicTweet
suggest_activity
suggest_activity_feed
suggest_activity_highlights
suggest_activity_tweet
suggest_grouped_tweet_hashtag
suggest_pyle_tweet
suggest_ranked_organic_tweet
suggest_ranked_timeline_tweet
suggest_recap
suggest_recycled_tweet
suggest_recycled_tweet_inline
suggest_sc_tweet
suggest_timeline_tweet
suggest_who_to_follow
suggestactivitytweet
suggestpyletweet
suggestrecycledtweet_inline
Add the following to ~/.var/app/org.mozilla.firefox/config/fontconfig/fonts.conf and reboot. The file (or fontconfig) may not exist so go ahead and create them.
<?xml version='1.0'?>
<!DOCTYPE fontconfig SYSTEM 'fonts.dtd'>
<fontconfig>
<!-- Disable bitmap fonts. -->
<selectfont><rejectfont><pattern>
<patelt name="scalable"><bool>false</bool></patelt>
</pattern></rejectfont></selectfont>
</fontconfig>