I believe there’s no lawful reason he can’t, as long as he doesn’t descend into defamation. It’s a civil action, not a criminal trial. They aren’t even any ongoing court proceedings. Moreover, commenting on the benefit the club brings to his electoral area is extraneous to the charges. No reason he couldn’t make that point in a way that didn’t expressly reference the charges, but impliedly did.
However, my point was more aimed at the fact he publicly commented on Everton (in a private capacity). Given he hasn’t commented on City, then commenting on Everton at all is questionable, given where his particular duties as an elected politician lie, and what interests he has been elected to advance.
It would be akin to the MP for a constituency with a car factory in it writing to the Secretary of State expressing about the closure of a car factory in another constituency because he drove that car.
Like I said, poor judgement at the very least.