I haven’t had any such issues ever anywhere. Not there either. Are you sure it isn’t coming from your device?
I’ve had it on both mobile firefox and desktop firefox on the 17-alpha-estradiol rapamycin.news thread
I’ve tested the link but haven’t had problems. Everything works fine.
And if I click a link to a pdf it shows, as usual, the file in the browser without downloading.
I don’t encounter the issue on a fresh install of Firefox on Windows.
Can you try on another browser? Is Firefox on your desktop and mobile synchronized (in case this behavior would be related to some setting… )?