As far as I know, there is no rule against quoting someone else's post into your reply, it is a feature made available by the forum and it's used by multiple members.
It's possible your reply was off topic ot it had already been made by another member.
If you provide a copy of it, that would help to decide.
So what happened is I gave a recommendation
https://bitcointalk.org/index.php?topic=5080741.msg48654587#msg48654587 and someone replied, quoting
https://bitcointalk.org/index.php?topic=5080741.msg48671930#msg48671930thanking me for the post that he learnt something new.
and then I quoted the reply also appreciating the person as is normal culture

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But alas! the next day, my post was deleted. That should be the 5th time or so my posts gets deleted in the Tech support thread and I really wonder what the moderator is really up to.
What is wrong with showing appreciation and what in God's name happened to free speech!?