It depends what you mean by endorse. For me, endorsing means recommending, explicitly giving a thumbs up. I have mentioned some of these companies by way of illustrating an article, that is all. I kept the language very neutral.
Nevertheless, I take the point that readers might assume that any mention is a positive thing unless otherwise stated. I’ll keep this in mind in future.
If you know of anyone, any idea, any company, anything, that represents a real challenge to the excessive commissions that many estate agents in Spain charge, then don’t hesitate to let me know by PM.