This happens not just with the M key, but with the other ones as well (e.g. HK + L to launch Logseq, also will skip my video).
This is a mild annoyance for YouTube, but triggering unintended letter shortcuts in other apps can be really a problem.
How do you guys deal with this/ fixed this?
For the record, my hyper key setup:
BTT Hyperkey actually works fine for me.
Have you tried the obvious things, restarting the Mac and all apps?
Otherwise there is way to use Caps Lock as a "real" modifier. Set Caps Lock to right control in macos. BTT can distinguish between right and left modifiers for shortcuts.
Hi @Frank1 - thanks for the reply. Hyperkey works for me too, it's just that it's bleeding the non-modifier key outside of the shortcut.
Can you try on your machine to:
Is your video still playing with sound, or is Mute triggered as well as the shortcut?
You are right. I never noticed that until now because I don't use Safari that often. This is probably a bug.
Haha thank you for checking & confirming!! @Andreas_Hegenberg, don't know if this is something that's already on your radar? (I'm on the latest MacOS update, if that helps)
Since I'm always looking for solutions that nobody needs... 
The m for mute in Safari only works in two fields, which logically do not accept text.
So if you set m = m (no) for these fields and adjust the Advanced Conditions, then hyper + m should not trigger the mute command. But actually ... nobody would solve it this way.
hmm but to me the M is just a symptom of leaking the key more generally outside of the desired key combination - e.g. it will also happen with Caps + L if you try that same setup (you'll get the video to skip a little).
there are several instances of this that happen to me as I work during the day, but just on YouTube, but also other websites/ apps.
(re your solution, I struggle to follow 
I'm not as technical as you are, so I can only observe the bahaviour and report on it)
@Andreas_Hegenberg any thoughts on this? the leak doesn't just happen with Youtube in Safari, but in other places (e.g. when I have Citrix open, none of the Hyper key shortcuts will work - it does happen in other apps too)
I don't know yet how youtube / some apps manage to get the key after BTT has intercepted it. I'll look into it soon.
For Citrix the issue might be different, I'm not sure about the current state - but for a long time it didn't support programmatically generated keyboard shortcuts at all.
Could you check whether the hyperkey leak still happens for you with the latest BTT alpha?
It's working now!! Man, you're the best. Can't believe how responsive and knowledgeable you manage to be!! Something to aspire towards.
Out of curiosity, how did you fix it?
