This issue of a limited notes field in the contacts app - while it seems like such a small one to most people - greatly affects many of us who utilize the contacts in our Gmail accounts to store a great deal of information (usually, I have found, due to the kind of work we do). Frankly, for me the limitation is important enough that it has affected and continues to affect which phones and tablets I purchase.
There are only a few Android phones that do not have this limitation. Fortunately, the HTC One M8 and M9 don't have character limits in the notes field of the contacts app. (If you've stood in a store and copied and pasted many times over to test this, you'll want to know that there's a simple tell I've found - the name of the contacts app. If it's called "People," as is the case with the Samsung phones, so far everyone I've tested has had the limitation. If, instead, it's called "Contacts," as is the case with the HTC phones, then there's no limitation.
Some have theorized to me that the phone manufacturers include this limitation knowingly in order to keep phones from being overburdened by data. I have a difficult time believing this, partly because I have approximately 10,000 contacts, and in the accompanying notes fields I store everything from copies of correspondence to research to articles related to the contacts. I've never come close to any data storage space issues related to this particular issue. By the way, there's a bit of a work around with regard to this issue, though it's nowhere near helpful enough to change my feature priorities when looking for a new phone - something I do every six months or so. You can use a PC to do your major notes field creating and editing - and as long as you don't need to make any changes via your mobile device, you can get along OK. That is, while you can edit the notes field using unlimited characters space on your laptop, then read everything in the app on the phone, any editing on your mobile device done in notes which exceed the limit is limited by the character limitation.
I love my HTC, but I probably would be using a Samsung were it not for this issue. I've spent some considerable time - and many different times - on the phone with people at Samsung about this issue. Most of the time, after lengthy back and forth conversations (most people don't fully understand the issue initially; then, once they do, their usual responses range from some level of disinterest to judgments about why no one should ever need to reach much less exceed the maximum), I rarely can get anyone in either support or development to even agree to mention the issue to the development teams with which they at least share company benefits.
This issue is one of several that restrict the phones I buy. Unlike many (I'm guessing, based on the number of phones built with the relevant specs), a micro SD card is important to me. The importance to me of that one feature narrows the phones in my market considerably. In fact, based on very unscientific research, I believe my desire/need for a phone with a micro SD card and unlimited space in the notes field of the contacts app limits me currently to precisely two phones - the HTC One M9 (my current phone) and the Sony Xperia Z. As to high-end tablets, I own a Google Nexus 7 because it doesn't limit the notes field, but I just bought a Sony Xperia z2 tablet (because it also has a micro SD card).
Fortunately for me, both the HTC One M9 smartphone and the Sony Xperia z2 tablet are top-notch pieces of hardware. I used to own a Motorola Droid Razr M - when it included an SD card - because it, too, didn't limit the notes field. But it no longer has an SD card.
Surely there is some way for the phone manufacturers to get rid of what seems to be a spurious limitation. I know, for me, at least it would give me the opportunity to purchase from a less limited market.