It would seem from my experience and a few others, that having crafting furniture (150k GP Item) is giving the +1 buff regardless of being in your mog house or not.
The problem didn't arise for me until level 99, attempting to do a 100 synth, which in WW is pretty much the only option. Even though I removed my Desk from Mog House it was effectively giving me the boost and putting me at 100, making it impossible to skill to 100. I did well in excess of 400 attempts, with things moved around before finally throwing it out. Got a skill up within 5 attempts after tossing it.

If you are still leveling your craft, I would highly advise NOT getting the furniture until you're 100. Avoid the time/gil/gp loss that I did.

i wonder if this falls into the realm of easily fixed, and thus will be fixed, or just the right balance of punishing higher players that he just leaves it forever?

Duly noted though.... Though as someone leveling a craft that realistically can't be leveled to 100, meh.

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