hmm... hmm... brake fluid will absorb H2O - get the fluid hot - boil out the H2O - spongy brakes result. Same with condensation (careful where you store your bottles of brake fluid). I don't think I would use anything but brake fluid in the container when bleeding the lines - even with a one-way valve - JMO! 
Completely agree Scott that the potential for issue is there. In (careful) practice, however, on cars and bikes have never had it be a realistic issue. Definitely don't just walk off and let the system set as you go to take a wizz or do anything else that takes a while. But once the line leans and bends a bit, even with a fully purged system, there's rarely continuous contact in your bleed line and (done right without delays) you're always pushing it downhill.
Dedicated catch bottle with its own one way valve eliminates any such concern. I've got a couple. Honestly rarely use them though. The visual of fluid in to fluid is an assist. On cars where I can't see the corners anyway I do use them though. Or the pneumatic vac assist bleeder.
Now, having said that, if you go to the store and see a fancy air/vac bleeder to run from the caliper end and think "oh, hot damn, this will be great for the bike" I'd suggest against it. They will agitate DOT5 fluid. That's very bad. Even for DOT4 the reservoirs on the bikes are so small it's very easy to pull them dry if you're not careful. Perhaps even worse is you can splatter fluid out of the reservoir when using them. Drops of brake fluid all over your paint. With the bikes we just have to go slow.
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Topic: Clutch Adjustment (Read 15693 times)