Is it against the ToS to buy through your own affiliate link (clickbank)

No it's not at all, I've done it twice. I think they frown upon it if you ONLY use your account to get products at a discounted price by buying through your own links however.

no it isn't

It's probably the only time you'll ever earn a commission from Clickbank.

While clickbank allows it, there are restrictions of its usefulness. In other words, they have payout restrictions requiring sales from numerous IP's not just your own, so while you may buy from your own link, you may not receive the commissions if you're new or not yet earning regular clickbank checks.

Secondly, I have seen many affiliates that state that for their set of Terms it is not allowed (even though Clickbank doesn't care). Now, I'm not sure if that is technically legal on the part of those affiliates - they may be bound to simply accept clickbanks terms. But i know many of them that prohibit you (in there TOS) from doing so though there is no technical way to stop you that I am aware of.

Most networks do not allow this practice and most vendors will frown on it - so keep that in mind. Sometimes it's not "what you can do" but what you "should do". And if you're an aspiring affiliate marketer yourself, well, just remember stuff has a way of coming back to you.

Most vendors on the clickbank circuit, however, accept this as a cost of doing business on Clickbank.

It's fine as long as it isn't the sole purpose of your account

People differ on the ethics/morals of doing it though.

A bit like many other things, like whether it's ethical/moral to use scarcity on digital products, buy/rent backlinks when doing SEO etc

Yes, it's okay to do that.

Its certainly alright to do it, Ive done it multiple times! Its a great way to be able to get alot of different products for atleast 25% of!

Clickbank does have a rather lax policy regarding this topic. Although they don't endorse it, nothing is stopping you from doing so. Just keep in mind that they have a minimum 5 different credit card buys (last I knew) to be eligible for cashing out. Even if you made 5 sales and all are from the same card, you still can't cash out but if you making 100's of sales per month then there is no problem.

No its not, but its mos def frowned upon by product owners.

Its better to look for a bonus package to what your buying to increase the amount of value you get when buying a new product.

Getter done!