There are a number of elements to your concerns re your neighbour’s tent to consider when writing to your committee.
You should reference the by-law/s (e.g. altering the appearance of the building) that your neighbour is breaching when you write to the committee outlining your concerns.
You should also ask the committee if approval has been given for your neighbour to erect their tent, unlikely as that may be.
Be prepared for the committee to ask if you have approached your neighbour to express your concerns. Until you do that the committee may not take any action or do anything about your complaint. Your neighbour may firmly believe that the tent’s functionality outweighs how ‘bad’ it looks or any safety issues.
You neighbour may also be breaching a local council law or development approval if they are using the tent as an additional room for accommodation. However, local council response to an enquiry or a complaint from you may be muted with an “it’s something for your community to sort out” response.
Unless it is made of fire-retardant material, the tent itself poses a fire safety hazard which has to be managed by the committee on behalf of the owners corporation. Your building’s fire safety provider would be able to assess the risk or if any safety standards have been breached by the erection of the tent.
May the force be with you.