I know water stops a bloodmoon spawn in a16, have tested this accross many servers, but that's been reported and reproduced. We have our players build 200 blocks from any water, but this is an interesting thing we haven't tried, The bedroll having an impact.
Mite have to do some testing with that one. We always assumed it was players having their base to close to the water, as in the spawn points being around 80 or so blocks away from a player on bloodmoon, if that happened to land in water, no zombies would spawn for horde night. Much testing on our server for that issue, but the idea of a bedroll also stopping bloodmoon spawn is something Ill be testing for sure.