Reselling keys and links to reseller stores. Do not use our site to resell keys, and do not post offers from stores which allow third parties to resell their keys or gifts. For example, do not ask others if they are interested in buying your leftover keys from a recent bundle purchase, or link to keys for sale on sites such as Kinguin, G2A, or Eneba.

https://www.steamgifts.com/about/guidelines

I don't know if talking about grey sites is a problem but you definitely shouldn't link to them as per SG guidelines.
I don't use it but I have read a lot of people on reddit who reported having received dupe keys and not getting refunds or taking months to get refunds with hours spent trying to reach and communicate with support so I would say no

I have bought multiple keys with them. But I had one issue. One day at random they charged me again a bought that I did weeks prior. I contacted theyr support and they returned me the money. But it's something that shouldn't have happen in the first place.

It isn't about platforms like this being reliable or not but about game creators not getting their share of the deal.

No

It's a black market

If you want to buy your keys from legitimate retailers use https://isthereanydeal.com/ to check prices.
Other sites can be like ebay - they let you buy from someone else and you never know where they got the key from.
It could have been a legitimate sale or bundle, credit card fraud or whatever.
Also, some sites like to charge you extra for "insurance" which may actually be illegal in some regions. But they don't care because they will get away with it 99% of the time. And the other 1% they can simply state it was a billing mistake.
So, beware where you buy your keys from.
Because one day a key (or hundreds or thousands) may be revoked by the publisher because they were obtained through fraud and suddenly you have a non-received on your profile.

Been buying from them without any issue, people in SG can be sometimes weird, so but your games whenever u want

I got some keys from there and they all worked without a problem but buying from unofficial key sites is like gamble.

Never had problems with them, and when in doubt always check trustpilot.

I've had bad luck. From around 5 experiences in total, literally every single one of them has resulted in an invalid key and Eneba not replacing it. Luckily the keys were cheap, but still. I've never had a keyshop be as bad as Eneba.

Plus they constantly have people putting in fake prices to get their games on higher listings, only to cancel all cheap purchases. It's a weird site all in all.

It is trustworthy as any other grey market website is, I had no problems with dozens of purchases made there. When there was a problem with key activation I always got a refund from their support. You can look at it like this - I got 100% of things that I have paid for, which is not the case with Humble for example who is an official reseller.

These sites are use at your own risk. Please don't make threads for grey market sites on SG as these aren't allowed.