Since I've had trouble being taken seriously at work before --- when I was perceived as too young for the post, so it's just a 'trial' because they couldn't get anyone else(!), when I was the short plump little lady with no kid (therefore not quite grown-up herself?!) in the midst of tall graceful amazonian moms, or when I was the 'girl' among all the men --- I do have a tendency to channel an older, slightly schoolmarmish persona through my clothes sometimes, when it comes to business dealings.
It also helps with the opposite problem --- of seeming too approachable to the girls in a gender-divided office, until they expect me to huddle with them at lunch and through coffee breaks. It gets unprofessional, and while I'm happy to hang out with the individual people outside work, I don't like to reinforce the gender lines in the office. Playing down the playful or feminine imperceptibly discourages that, I find --- no one ever remarks on it, but they don't automatically assume I'm going to hang out with them; on the other hand, the boys feel they can talk to me better than someone with a more 'feminine' aura. Of course, I don't like the stereotyping either, though I'm taking advantage of it there!
I can't say I like to dress more mature or stiff or bland, though. I'd actually prefer to dress more age appropriately, with a little whimsy and a more colourful palette --- and with a little bit of the maverick and hell-raiser I am in private life showing through the obvious shyness and introversion. Indeed, I've gotten increasingly impatient with dressing for two faces.
I don't hold back my 'gentler' (read: sympathetic, tolerant) side at work --- even if old-fashioned bosses think I should; so why should I avoid the 'feminine'?
I'm passionate about gender and social issues --- I don't hold forth on my political opinions, but will *not* prevaricate or equivocate if asked; so why shouldn't my dress also reflect that I'm a bit of an outlier?
In my non-business aspect, I do dress a lot more casually and a little more colourfully, even experimentally --- oddly, for a shy person, it works really well to take the focus off me and shift it on to my clothes or bracelet or bag, even as it boosts my confidence and outgoingness! I used to do that at work too when I was younger; but found it can be counterproductive --- I rail against that, but I live in dread of losing 'authority' again because of it!
Have to find a middle ground, I guess, and I've just started trying.