How to sniff out fake time travellers 101:
- Inconsistent stories
- Avoiding answering direct questions, or answering like a politician
- Vague explanations
- Not able to explain themselves or their actions very well
- Using time travel itself as an excuse for their poor explanations saying it will "cause this" or "this" to happen.
One thing is for certain, and another is a speculation.
1) If you travel through time and remain time locked in your timeline, there is literally no reason to change anything in the past. Why? Your society has advanced enough to the point of time travel. If you change your direct past, the future you know may not happen, why risk destroying everything? There would be no reason to go back in time to let people know "time travel exists". You have no clue what type of adverse effects you can cause. It would be the feeble attempt of a mad man to make the present "more perfect" than it already is. Perfection is an illusion. If all that existed was perfection, how can you compare that to anything else? You would slowly start to feel nothing. That's why Utopias don't exist, it doesn't provide a species any drive to advance or evolve.
2) If traveling through time makes paradox impossible, then it presumes the multiverse theory and you're time travelling to an alternate dimension. Again, no reason to do this, because you cannot affect your time in any fashion within your universe, so the outcome remains pointless.
Yes it's an interesting topic, there is potentially validity to it, but any evidence will remain top secret until the government decides society is ready for the technology. This could be in 2028 like time travelers predicted, or it could happen generations from now. Technology advances too quickly in order to effectively test practical application, then safely release it to the public. There is so much disinformation out there on this subject, that any TRUE evidence would slowly be introduced within the mix of misinformation and eventually be "discovered" as truth by the public. Therefore, everything is questionable, and should be scrutinized with a healthy dose of skepticism.