Hello remaniki and sorry for my delayed response! I was wrapping up the 30/30 Hub Challenge and have been very busy lately. My opinion? It really depends on the situation. For the situation you have stated above it is ok to share the link because you are sharing the person's Hub article, not just the question. Anytime someone answers a question we ask in Hub form, HubPages automatically links the Hub to the original question asked. There is absolutely nothing wrong with sharing other Hubber's Hubs!
As far as other situations, it can be difficult to say. If someone is soliciting a question or wants to learn more about something you have written you can consider sharing your link. As Wesman Todd Shaw has stated, you Never want to post your Hub links in the forum because it will be considered spam and you could get barred from HubPages.
I suggest you use discretion when sharing your own links. I do so only when I think it will benefit the reader and that they might be looking for more information on the subject. Sharing your own Hubs with Social Media is a great way to get backlinks to your Hubs as well as getting more traffic.
I hope this gives you a better idea about sharing our own links!