So in astrology, your Midheaven is your public persona. How people will see you before they meet you is determined by the Midheaven. Online, your Midheaven will be shown because it’s your internet persona! And the internet is very much public.
When you type or message people, depending on the situation, your Moon, Mars, Venus, and/or Mercury will shine. If you’re having an important, emotional conversation, your Moon will be shown. If you’re having a heated, online debate, and you’re mad, use Mars. And how all of your expressions will be made will be through your Mercury. If you’re sexting or flirting, your Mars will show ;)
Also, look at the house where your Mercury is in. The House your Mercury resides in will affect how your Mercury will be expressed! Also look at the house placements for your Moon, Venus, and Mars to a smaller extent!
However, planets aren’t the only things to consider! Consider your 3rd House and the 10th House. The 10th IS the house of the public persona. Consider the planets in there. Planets in the 10th House can add a “flavor” to the Midheaven. Look at the 3rd House to see how your methods of communication can change. For example, I have a Pluto in the 3rd House in Sagittarius. Although I can think very optimistically, there is also an obvious skeptical, investigative nature to how I think. And since the Internet is essentially our thoughts, this can definitely be seen online! Apply this same method to the 10th House!