I don't use core for transactions for a long time. Not safe. If there would have connect a Android device with Trezor option I might use my XT node for transactions but since this will probably not happen MyCelium works just fine. It even has integrated BTC to SEPA in it... So why use a node for transactions?
Not very smart of you.
1. You can be tricked into believing a transaction has been confirmed when it is not.
2. You leak information about which addresses belongs to you to full nodes you are talking to.
You can't use it of a phone.
It used to run fine on N900, but the blocks are too large now. You statement will be true in the future as well if the block size is increased.
And now what is spam? How do you know that? Who give you the right to decide? If you don't like it don't run a node. Are you a bank? Are we going the way banks are going? And how will users know so they will not be blocked.
Any node can make up its of mind about what spam is, and have the right to decide it. There are some default filters, and some of them can even be adjusted by command line options. If you don't like it, use a bank. If you use an SPV wallet, the random full node it talks to will decide for you if the transaction you are about to send, or one you expect to receive, is spam or not. Users won't know what the policy of an individual full node is. The average policy of the network will be estimated by full nodes, and translated into fee and priority estimates. If you run a full node, you will know what is required to get a transaction confirmed with good probability within a given number of blocks. If you send from an SPV wallet, you must trust the defaults and the full node you are talking to.
And just to be sure. There will not be 2 Bitcoins after hard fork. If it happens 25% will change to bigger blocks or will be killed by bitcoins tht are useless or even 51% attacks for sure... So saying there will be 2 and big problems is BS. When first big blocks is mined small chain will die in hours or days... Unless there are more exchanges and wallets on it. Than it might take longer or it might even manage to beat big one since miners might change back to it. But there will never be 2 Bitcoins for a long period time... Just look what happened with LTC and FTC.
Remember the last soft fork (BIP66)? We had a six block chain split after the fork because F2Pool didn't take the time to verify the blocks it got before building upon them. Why didn't they verify? Because it takes time to verify a 1 MB block. Why was this a problem? Because F2Pool announced support for the soft fork, while actually they didn't. Now try with a hard fork to even larger blocks.