bitcointalk.org will never hold people's money like that, even temporarily. Perhaps someone else could set up such a hub, though it's really sub-optimal. For now, on-chain fees are low enough that on-chain transactions are probably better, though fees will eventually rise again; hopefully by then some new tech will have either improved LN in this area or provided a good alternative to LN for these use-cases.
Having an on site balance feature to tip people is simply a horrific idea. For starters keeping aside the whole Doge Coin Tip bot fiasco that broke down around a year ago (a repeat of which I doubt will happen since the owners to put it simply were foolish investors or thieves whichever you may take it to be. The administration here doesn't seem to fall in either category
Issues
- For starters the biggest issue would be the fact that people would start using the onsite tip function as a wallet instead of well what it should be, a tip function. Given this site also has a marketplace section people will end up doing trades with on site balances (this pretty much has become the norm in most places that do have a tipping feature). Holding huge numbers would be rather risky for both parties
- Time wasted on a non essential feature. From what I understand the "New Forum" is in development since ages and people would much rather have that instead of a tip function which won't see much use (merits are free and yet it's rarely given, not to mention merits giving on forum rank boosts has lead to people exchanging it for personal gains which has artificial pumped the stats on how many merits are given).
Proposal
Add a donation button linked to your bitcoin address. As in the button can be shown at the bottom of your post or near your profile but all it does is just open your bitcoin address as a link like:
Which pretty much serves the same purpose as what Theymos suggested AKA just use the chain to donate. This will just make stuff simpler than going to the profile and from atleast what it seems to me will be much simpler to implement