<p><em>(I'm transferring my comment so that this doesn't remain 'unanswered'.)</em>  </p>

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<p>I really don't see a problem with leaving a comment to the other user, perhaps under one of their questions, noting that you appear to have similar interests and would be willing to talk outside of the site about them.  You can have external contact information listed on your userpage that would allow them to reach you.  If you don't want personal information just sitting there, you can also wait until you have established that they want to communicate, and are currently logged on, and edit your page to provide your email address, and then edit again a couple minutes later to remove it.  </p>

<p>I recognize it is true that the SE system is a bit ambivalent about comments.  Comments are <em>supposed</em> to be transient and only used to prompt people for clarification, for example.  However, comments are quite regularly not used that way, not only here, but on many sites including meta.SE.  If comments that are not really relevant to a thread are flagged in the future, they would be deleted by the moderator team, but they can be undeleted if needed and it seems more likely that you would have deleted them yourself long before then.  </p>
