Ok there are some missleading information shared here....
If a HT has 10k people using it that DOESNT MEAN you need 10k likes to rank for that HT....
There is no difference between using 10-15 HT and using 30... i still see a lot of post ranking on explorer and top HT using 30 HT on post (not even on comment) so that theory is wrong.
ITs a good OP advice to escalate your HT if you are getting tons of likes go ahead an use harder HT there is a chance that you can get on the TOP post on THAT HT but that doesnt mean you will be on EXPLORE, those are 2 different things.
People use HT on comments to avoid being seen as a spammer by the user (thing that is not proved also) i dont hear ppl complaining about HT... that its just a paranoic thinking of us the marketers using IG....
You can use HT on comment and on post it doesnt make a difference.