Epistemic status: much ado about nothing.
tl;dr: I look at people saying “I’d bet” on the EA Forum. I find that they mostly mean this metaphorically. I suggest reserving the word “bet” for actual bets, offer to act as a judge for the next 10 bets that people ask me to judge, and mention that I’ll be keeping an eye on people who offer bets on the EA Forum to consider taking them. Usage of the construction “I’d bet” is a strong signal of belief only if it is occasionally tested, and I suggest we make it so.
Having specific wording for people to indicate that they literally want to make a bet seems fine, but policing ordinary language use in an abrasive and unwelcoming way is a very bad idea. EA will be much more effective in its stated goal if it is accessible, welcoming, and friendly to new people--and people who want to talk like normal people.
I agree that you are pointing out a downside, but I think that the tradeoff is small, and the benefits of increased betting larger.