If I've already written something I feel to be relevant to what the OP has said, or to elaborate upon my own thinking in my comment then I'll drop it in with my comment as a link — especially, if what I wrote was long and copy-pasting it into my comment would result in a ridiculous hijacking of visual space when expanded and/or it contains images and/or further links.
And, if others drop links in their replies to me, so much the better — I can follow their immediate train of thought without getting bogged down in the detail and explore the rest as and when I wish.
If someone were to simply spam my post(s), I might feel a bit affronted, but I could simply remove those comments without presuming to lecture them on netiquette — I don't pay Medium for the privilege of allowing comments on my pieces, so they could spam me a hundred times in succession and, whilst it would be tedious to remove them all (and I'd certainly block them after that kind of behaviour), it wouldn't actually make any difference to my post or any of the comments left by the other 4.5 people who read my nonsense, so I see no reason to get upset about even that.
If the commenter is a cartoonist or other kind of artist and their reply best expressed in that medium then they really have no option but to link anyway — blanket blocking/removing links prevents interesting discussion with those people and is, imo, shortsighted for the sake of stroking one’s own unmerited superiority complex.
Some people (mostly those with little ground for actual self-respect) are seemingly overburdened with self-esteem and take umbrage at being 'disrespected' — narcissists and/or other Cluster B personality disorders figure prominently amongst them. They have an inflated sense of the significance of their own writing — if it really were that good, they wouldn’t be trying to scratch for likes on Medium, would they? I haven’t seen any of the genuine ‘names’ I’ve encountered here … those whose work is available from Amazon/somewhere-else-significant … and who are interviewed/spoken of in magazines, newspapers, etc., asked to take part on discussion/conference panels, etc. … take anyone to task for posting a link with their reply. I’d suggest those who object were fatuous, vacuous, pompous, condescending ¹ windbags, up themselves (or even worse), but I’ve had my knuckles wrapped for that kind of thing in the Past and am on my final warning for some reason or other that Medium hasn’t seen fit to clarify, so I refrain from doing so these days.
If I have any complaint about people's response to links in my carefully worded and constructed, yet criminally underappreciated, ouevre, it's that they don't follow the links in my own posts and in my comments in reply to their comments on my own posts — for a site for readers, Medium sure does seem to attract an oddly large number of people who don't seem to want to read *sigh*
Hey ho ... seem to have managed to reply without dropping in more than one link, so that's something at least, I suppose ☺️
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¹ That's when you 'talk down to' someone and explain things they already know (or might reasonably be assumed to know) .
It's a bit like being patronising ².
² Which is a simile 😉.