I urge that 0% commission is harmful.
(though I think 0% commission is a good strategy for small validators to promote themselves)
However, I think security is not the main point of 0% commission problem.
Even 0% commission is forbidden, there are lots of incentives which makes validators invest security less before we solve the asymmetric information between validators and delegators.
(So I think the proper solution of security problem is slashing.)
Nevertheless, I think there are 2 possible negative effects.
One is that could make the non-technical community members ignore costs of node operation. (It is the problem which @syncnode mentioned )
I think this problem is not a big deal, because it could be solved by simple nudging, for example, prompting (community tax rate + commission rate) in place of (commission rate).
The other and more important problem is that 0% commission is very strong disincentive that (especially whale) atom holders start to operate their own new validators.
As @kwunyeung says, inflation is a punishment to the atom holders not bonding their atoms to the network. Likewise, commission could be a good punishment to the (especially whale) atom holders not operating their own nodes.