Is my computer really infected, or is this a false positive?

Rootkit.HiddenValue@0 HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\FlashUtil64_11_6_602_171_ActiveX.exe\DisableExceptionChainValidation

I looked at the value of the registry entry, and it was simply “0”.

Is the mere existence of this registry entry evidence of a rootkit? ???

It looks to me like a FP but please submit it to the Comodo for the analysis.

Should I do “Ignore → Report this to COMODO as a False Alert”, or should I submit this some other way?

Yes you can. After you submit it via CIS as you said you can make a FP topic here on the forum:

Or you can submit it here as well:

If you still want to know for sure if it’s a FP… It would be good to double check the file in: (You can also submit it here… Comodo will get the file)

Welp. My computer restarted while I was sleeping, and it scans as being clean now, so maybe it was just something I had open at the time. Very strange!

Could be anything. I don’t think it’s down to this detection. I see. In that case you are safe and it’s def FP. By the looks of it… It’s an error or conflict with Comodo AV and Flash that’s why you got this FP.