This is a really great add-on! Ii do have a couple cases where I have to turn it off to get something to display correctly. Almost everything else is much better because of it, and most messages from my bank are fine but I have a few recurring messages from them that I screen capture for my records and while the email loads I can see it until it finishes loading and it all disappears. I don't mind this and It's not really a complaint, just something I find odd. It's very simple to switch it off for a few minutes to do what I want to do then switch it back on for everything else. Thank You for making it, it is appreciated.

2nd Update: changed rating back to 3 stars. Dev never promised the feature I needed. Add-on is working as described.
UPDATE: change from 5 to 1 star: I should've reloaded the page first... What I wrote below is sadly not true - once Trimless get to work, all the highlights are gone. So I had to uninstall it right away. /UPDATE
Thank you so much! This saves me so much time and energy at work! In short: I need to use the search field in Google Mail to filter emails [seriously the only way to do that task; I've worked on it for weeks] -- those keywords then get highlighted inside the email, which makes scanning dozens of emails feasible. If I have to click the link to open the whole email in a new tab I lose that highlighting function! Of course, since this is a use-case Google doesn't consider, they just don't implement an option to simply show all emails, no matter how long.
(Btw, it's still working; I'm using FF ESR 91.10.)

Thank you! but still trimming when replying in the textarea.

it was working perfectly beofre but since 5 days ago, it stop working ... with latest firfox
hope there will be any updates to fix it
thanks !