Holding on to your shares wouldn't necessarily be a charity. It could be very profitable if the share price increase as a result of investment from the Comers, increased turnover and success in the league.
How excactly will the Comers put money in to the club? It's only fair that they don't pay a higher percentage of the total amount invested than their percentage of ownership. I would think that the way they will do this is by issuing new shares. Shares that they offer to current shareholders, but if these shareholders don't want to invest further, then the Comers will buy the shares themselves. And own a higher percentage of the club as a result of this.
Fans that also own shares would then need to spend more money on new shares, or alternatively see the value of their existing shares decrease due to there being more shares available. I don't think most of the fans that bought shares did it because they saw it as a business investment at the time. I didn't buy any, but it would be an emotional investment rather than a business investment if I had done that. I wouldn't be too surprised if the Comers are planning that the fans will make that emotional investment once more.
Alternatively any increased investment for players etc will need to come from the club itself. That means borrowing money as the club don't have any atm. And any loan would in the end be payed back by the fans through higher ticket prices, etc.