Here's my take on it (being the mod that had the conversation with Pekka).
We have a very clear policy on LMGTFY links. What you're doing doing is LMGTFY without the LM, the FY, and the link.
So where's the value that you're adding here? If anything, you're taking the pageview away from Stack Overflow. Additionally, if you've taken such care to Google the result and make sure it was directly pertinent to the question at hand, why not turn that into an answer?
It should also be noted that Google won't always return the same results for two separate users. Robert Harvey and I actually came across this issue while chatting, I posted the results for a Google search, he posted his, and the order of the items was reversed (we were each referring to the "first" result, only to find they were different for each of us for the same exact search term).
Of course, over time, links will rise and fall changing what is shown in the top few results, and those links might not necessarily answer the question at hand correctly anymore, rendering your search suggestion moot.
If we want Stack Overflow to be the canonical resource for Q & A, then if you're going to make a search suggestion in the comments, then that comment should be canonical as well. The fact that it's not a direct link prevents it from being canonical over time (granted, not everything is immune to the effects of time, but there are things we can do to make it more immune).
If you're just going to leave a comment, then the best thing is to add a direct link to the resource that you feel answers the question. If you don't, it's very possible in the future that what you see now is not what will be shown to the user later. The web is in no way a static place, and while links do die, the volatility of a search term suggestion seems much higher than a direct link to a resource.
Specifically to your second point, if the link is to another question on Stack Overflow that answers the question, then you should be casting a vote to close as duplicate (assuming it is a duplicate).
If it's an exceedingly trivial question that borders on it being closed (or is an outright candidate for closure) then why not flag it or cast a close vote?
The point is, if you're going to take the energy to perform the search and find out what the best answer is, there are much better options that will benefit the site overall at your disposal than leaving a comment which just says "Google this".