We should only recommend software we actually used ourselfs to make sure we know what we are talking about.
It is ok to recommend a tool we did not use in a comment like here or even recommend a specific google search term to find possible suitable software?
Try to avoid that as much as possible. You're still just putting an answer in the wrong place, even if your intent is to try to give a bit of useful information presented in a less valuable way.
Because the comments are useful, they tend to get up-voted and not flagged, therefore not removed, and become a self replicating problem. People see them and follow suit, and then we start seeing more discussion than we really want to have. This was a bit of a problem on Pets, and still is to some extent.
If you think that someone has arrived with a question due to not really knowing what they could have searched for, it could be appropriate to guide them to some extent in comments, but only in an effort to help improve the question somehow. Maybe they'll be able to scope the question better if they see a different set of results.
In most cases, try to avoid it, it can become very difficult to control later if the practice takes hold.
At least if the question was already staying around unanswered for some time, I feel a comment-hint can be useful, if used correctly. Think of the following:
I have not used it myself, but would XYZ (link) fit your needs? Please give it a look and report back. If it does, feel encouraged to answer your own question with it, including a short description and arguments.
This would be a double win IMHO: The questioner does not feel "ignored" (so it's good for the reputation of our site), and if (s)he comes back and does as asked, the real answer will be available to future visitors. If (s)he comes back and just leaves a comment, the "original commenter" can – depending on the outcome – post the answer, or delete the comment.
We should only recommend software we actually used ourselfs: I wouldn't make that a law. Sure, that's the best and recommended way. But if I know a software exists, fitting the OP's description, and has good reputation (e.g. I know people using it, have read "objective" reviews, or got the clear impression in other ways), I would make that an answer.
You should not post an answer as a comment. While answers based on direct experience are encouraged, if you know of a product that meets the requirements, please post it as an answer. Indicate the extent of your experience if you think it's relevant.
On the other hand, if you've found a product that may or may not match the requirements, do not post it as an answer. (Counter-example: XMPP client with OpenPGP support) If you aren't sure about the answer, then further investigation is needed. While this investigation is underway, it's ok to post a comment, either stating that you are performing the investigation or encouraging others to perform the investigation. The person who completes the investigation should either post an answer, or post a comment explaining that the product is not suitable; then, either way, flag the comment as obsolete.
Basically, do not post answers that are tentative regarding the fundamentals. It's ok to post an answer if you know that the core requirements are met and aren't sure about some of the nice-to-have features.
