I know I’ve paraphrased this dozens of times, but here it is written out semi-formally - Boyd’s Law of Blog Link Acceptability:
Any link is acceptable to the reader provided it is relevant in context and adds clear value.
OK, so I didn’t invent this - other folks have been saying similar things for years about web links in general - but the title sounds cool 
“Relevant in context” means that it makes sense - the linked material is directly related to the whole post in general, and the particular point suggested by the linked text. There are no unmet expectations or surprises. “adds clear value” means that the link is not there for the sake of the link but actually adds value to the reading experience. This applies equally to blogrolls, links within posts, and links within social linksharing applications.
What do you think?
Is it worth commenting simply to answer, “I agree”?
Hi Lani,
absolutely
I’m glad someone did 
Best regards, Andrew
I agree too - I am glad we cleared this up because often I don’t comment because it has already been said or seems like 50 others have said I agree.
Hi Trish,
thank you for your comment. I think it is all about adding value, but you should always feel free to leave “me too!” comments here
Cheers, Andrew