They're part of a usergroup that gives them the title under their user. Whether it means or does anything, I don't think so. I've seen people with it who just have it for fun.
I'm Petros, the Speaker of the Model House of Commons.
Basically the parties of the MHoC as well as any independents can run in a TSR General Election which happen roughly every 6 months. There are 7 parties (Labour, Tories, Liberals, UKIP, Greens, Socialists and Libertarians) and also currently 1 Independent MP.
There are 50 seats in our House of Commons which are distributed by percentage of the vote (it uses the D'Hondt method, but that's going into a little too much detail for now), so you need 2% of the vote for 1 seat.
There is going to be a General Election at roughly the same time as the Real Life one to hopefully encourage new members like yourself to join a party or stand as an independent and to more importantly get involved.
If you have any questions, I'm more than happy to answer them