OK, after listening long enough, I can hear the periodic FSK as well.
The carrier disappeared at 0653z. It looks like it went off, vs fading out, but as the signal was getting weak at that time, it is possible it faded out.
After consulting with some folks in #wunclub, it sounds like this is a 300 baud 750 shift RTTY transmission, possibly from the UK. Although if mapleleaf is hearing it 24/7, I'm not sure if that fits a UK QTH.