It seemed to get a resounding yes from many of those who answered.
Personally I say, NO! You should not assume that the author of a hub will automatically accept your comment which is merely a possible plug for your own hub or website. To do such a thing is plainly spamming the Hubber.
By all means you can mention that you have a similarly themed hub, a hubber may ask you to provide a link or may go to your hub and link to it themselves. If they do, be fair and reciprocate.
Do not though post a hub link into a comment capsule. HubPages doesn't allow it and it is not really proper etiquette for the site.