A message forum for general discussion. Please come and chat with others!
The question of professionalism would probably depend on whether the items posted here are the same type of writing as you're offering to write for potential employers. OT work would be OT.
The site provides the Ink Spot option for showcasing items to outside viewers -- see InkSpot.Com Setup from Writing.Com 101 for details.
OTOH Posting work here that was done for hire runs the risk of appearing to be an ad = spam, which is against the site rules. You also cannot post anything you do not own the copyright for.
Most members here do creative writing. Most of them are hobby writers.
Most of the few members I know of who work/worked in the industry, use WDC for their personal creative works.
Some submit work they've posted here to publishers. Some self-publish.
Generally those who intend to publish will use access restrictions on their items to avoid them being labeled as previously e-published by publishers, even though WDC does not consider itself to be a publishing site. You'll find those settings in the Advanced section of the item create/edit page. The same settings can be used to take an item private that has been submitted or accepted for publication. Also, on WDC items can be deleted at will, and some members only have work posted here while they're getting feedback for a WIP.
Hope that helps.